Note: This post builds on a previous YLE post that explained what’s going on. If you missed that, start here.

1. Can you just tell me what not to eat?

Unfortunately, it’s not that easy, because a source hasn’t been confirmed. So risk falls on a spectrum and risk tolerance varies.

This is how I’m thinking about it:

Skip bagged salads, salad kits, and boxed salads from the grocery store, and avoid them at restaurants and fast food places, too. Michigan’s warning on Monday (unusual to go public before the FDA) is a strong signal of what they’re seeing. Whole heads of lettuce are fine if you strip the outer 2-3 layers, since that’s where contamination is most likely to sit.

Michigan’s investigation has yet to pinpoint a company or rule out other foods. Two dozen other states are still under active investigation. So avoiding other foods is reasonable. In previous outbreaks, the culprits were raspberries, fresh herbs (basil, cilantro), onions, and snap/snow peas. I would still avoid these, especially if you’re high risk (pregnant, older, or immunocompromised).

Stick to produce you can peel or cook. (If you have frozen berries from January, you should be in the clear as this outbreak likely started in May.)

2. How long do I need to cook produce for? Does freezing work?

Cooking food to an internal temperature of 158°F is the only thing known to kill Cyclospora. This means sautéing raw spinach for about 1.5 minutes. (Turn your salad into a stir fry!)

Microwaving doesn’t work as well because heat spreads unevenly; research shows 45 seconds wasn’t enough to kill Cyclospora, so go longer and check that every part, not just the surface, is steaming hot.

Freezing isn’t reliable because a typical home freezer isn’t cold enough to kill the parasite. Research shows you’d need -20°C (-4°F) for at least 2 days, or a commercial deep freeze at -70°C for an hour, well below what most kitchen freezers hit.

Washing helps a little, but not entirely, because these microscopic parasites love to hide in the grooves and crevices. They also hide from home remedies people suggest, like lemon juice.

3. Is local produce better than big distributors?

The risk is much lower. In fact, there has never been a documented cyclosporiasis outbreak linked to a local farm.

That said, Cyclospora lives in soil and contaminated water, so a local farm could be affected if it shares a water source with a large commercial farm. Cyclospora can also enter the food supply at a packing, processing, or distribution facility, where outbreaks get amplified—a local farm would be safer on this front, too. My hunch is that the real culprit here isn't the farm itself, but distribution, but we don't yet know yet.

4. How much precaution should we be taking in California (or other states), where very few cases have been reported?

Distribution networks are complex, but all states are now actively looking for cases. That makes me more confident that states with low case counts (that stay low) aren’t linked to whatever is driving the outbreaks in Michigan, Ohio, New York, and elsewhere.

All states have some cyclosporiasis cases, but that’s expected: it reflects multiple outbreaks happening at once. California, for example, has cases, but not more than in past years—actually fewer. About 95% of California’s cases have involved people who picked up the parasite while traveling outside the U.S.

For what it’s worth, I live in California, and I’m not eating lettuce but being liberal with the other foods. I don’t have time for weeks of exploding diarrhea, but my guard is a little more down than it would be if I lived in Michigan or New York.

5. How do I know what bug I have?

Many bugs can cause diarrhea. Norovirus is a common virus that spreads year-round and causes similar symptoms, but is highly contagious, while Cyclospora is a parasite that is not contagious from person to person.

To differentiate between the two at home, it really comes down to symptoms and timing. If symptoms show up within a day or two and pass quickly, think norovirus. If it lasts more than a week and then it comes and goes for weeks, that’s likely cyclosporiasis. Antibiotics help with cyclosporiasis, so it’s worth getting tested (although I hear the test is expensive).

6. How does this end?

Once the product is out of circulation. That can happen naturally (e.g., clean salad gradually replaces infected salad), through intervention (stores pull it), or as the season shifts toward fall, since cooler, drier conditions make it harder for the parasite to mature.

I don’t know how long it will take to end. No one does. But the Cyclo season typically ends in September when the parasites can no longer mature as efficiently.

7. There is no federal guidance for us physicians. When am I supposed to test and how?

It’s absolutely insane how long the federal Health Alert Network (HAN) notice was delayed, but it finally came out yesterday. Michigan’s provider bulletin is absolutely fantastic. If you’re a clinician, read that.

8. Can our animals get this?

No. Cyclospora only infects humans and spreads solely through the fecal-oral route. Researchers have tried to infect chickens, dogs, mice, rabbits, monkeys, and several other species in lab studies, and it hasn’t taken. So feeding your salad to your chickens is fine.

9. How easily is it transferred within a restaurant kitchen, like if a cook has unknowingly handled contaminated lettuce or something for someone else’s order and then touches your food? Or via cooking utensils/equipment/shared prep surfaces?

If the produce arrives at a restaurant already contaminated and is infectious (which takes about 2 weeks on a head of lettuce, for example), and then that lettuce touches a cutting board, knife, or bin used for other food, the parasite can be transferred. It was great news to see Taco Bell move quickly last week.

10. Is there any hope of CDC or any of our government agencies tracking down the source of this outbreak? Does the EIS have the resources to find the source?

I’m confident that the federal scientists are doing the best job they can do with what they have. Cyclo is difficult to investigate because it takes so long to cause symptoms (do you remember what you ate 10 days ago), it takes an enormous amount of resources to pinpoint; some foods, like at Mexican restaurants, have many ingredients; making it challenging to pinpoint a single ingredient; and testing options are limited. There were definitely outbreaks in the past where no source was found.

Local and state public health departments are also working their tails off. But public health, and specifically parasitic teams, have been chronically underfunded. They are holding on by scotch tape, and now, with the largest cyclosporiasis outbreak in history, they are overwhelmed. While resources can be pulled from elsewhere, public health departments are also dealing with record cases of measles and whooping cough on top of travel-related Ebola and the World Cup, and everything else. It’s a lot.

Communication, guidance, timeliness, and transparency are what the federal government is falling short on. There has been very little communication, and what has been said is that these outbreaks happen all the time. This is not normal, and saying so without communicating what the public should actually do is unhelpful to the point of gaslighting.

Bottom line

There are steps you can take to reduce your risk during this big foodborne outbreak while the systems around us catch up. I will be back when we know more. Keep your questions coming!

Love, YLE

Your Local Epidemiologist (YLE) comprises a team of experts, ranging from physicians to immunologists to epidemiologists to nutritionists, working together with one goal: to “translate” ever-evolving public health science so that people are well-equipped to make evidence-based decisions. The YLE suite of newsletters reaches over 475,000 people across more than 132 countries. This newsletter is free to everyone, thanks to the generous support of fellow YLE community members. To support the effort, subscribe or upgrade below:

Subscribe now

I know a lot of you have questions about the Cyclospora outbreak. The YLE team is collecting them all, and tomorrow I’ll pick the top 10 for a deep dive. As of this morning, there is still very, very little communication from HHS, which is pretty insane.

In the meantime, here’s what’s going on with health this week, including other bugs like ticks and mosquitoes. Expect trucks to be spraying insecticide soon, and let’s celebrate an enormous public response to a new proposed federal rule.

Disease weather report

Cyclospora keeps climbing

Cyclospora cases continue to climb. Some of this is expected, since more people are now aware of it and testing for it, but it is still an undercount, given that many people wait out the sickness at home.

The total number of cases is hard to pin down. This is because data in the U.S. is decentralized (local health departments report to states, states report to the CDC), so you will likely see numbers all over the place. If we scrape for state-level data, the most cases (2,640) are in Michigan, followed by New York (470). A local health department in Northwest Ohio is reporting 661 cases.

While there are cases in over 30 states, the U.S. sees cases every year, often from different outbreaks. A key question is whether the number exceeds expectations and, if so, why. In some states, this is certainly the case. For example, the number of infections in Michigan is 31 times higher than in previous years, and in New York, it’s three times higher. In some states, like California, rates are not higher than normal.

Michigan’s health official announced yesterday that preliminary findings indicate lettuce or packaged salad greens as a likely source. The investigation has yet to pinpoint a company or rule out other foods. Two dozen other states are still under active investigation. Zero word from FDA.

What this means for you: Continue to avoid bagged and boxed salads at grocery stores and restaurants. I’m still sticking to produce that can be peeled or vegetables with smooth surfaces, like cucumbers, until more data comes in.

Ticks are backing off

We’re well on our way down for tick season. Activity tends to drop off as we move deeper into the heat of summer.

Why? Ticks are prone to drying out, so in peak summer heat they retreat into moist, shaded leaf litter rather than questing (climbing grass to grab a host), which reduces host-seeking activity even if the tick population hasn’t shrunk. This dip also lines up with the tick life cycle: nymphs, responsible for most Lyme transmission, peak in late spring/early summer, then quiet down in the hottest weather before adults pick back up in fall.

Mosquitoes taking over

As ticks recede, mosquitoes take over and with them, the rare diseases they can carry. The most common one in the U.S. is West Nile.

Peak mosquito season is still about a month out, but the CDC is already flagging an unusually early surge in West Nile virus (WNV) activity this year. They have flagged 48 cases across 23 states detecting the virus, which is more than five times the historical average for this point in the season.

What this means for you: Most people infected with WNV never even know it because ~80% have no symptoms. But older adults and those who are immunocompromised can develop serious neurological illness. Start being consistent with using an EPA-registered repellent (with DEET or picaridin), dumping standing water around your home, and using screens at dusk and dawn. You may also start seeing mosquito spraying trucks. (See more below.)

Heat blanketing the North

This week, a large swath of the northern U.S. is facing the most extreme heat risk category. If you’re in the purple or red areas, everyone is at risk and needs to take action. Heat kills more people in the U.S. than any other weather event.

What this means for you: Check on elderly neighbors and relatives, hydrate before you’re thirsty, and move strenuous outdoor activity to early morning or evening if you can. Here are 6 things to know about heat-related illness from the YLE team.

World Cup Health Security Center Update

We’re nearing the end of the World Cup tournament (the final is on July 19!), and there have been no major outbreaks tied to the games, aside from heat-related illness. A few teams reported minor illnesses among players.

Measles remains the primary focus of monitoring. There are a number of cases passing through major airports (far more than in any other year), particularly near the World Cup games. While it will be very hard to track, we could very well see outbreaks across the world following the World Cup.

Spotlight: Why is that truck spraying my street?

With mosquito activity picking up and the U.S. having a particularly bad start to the season, you may start noticing spraying trucks in your neighborhood. Where they go is driven entirely by your local public health or vector control department’s surveillance data. Departments set traps to collect mosquitoes, send batches to a lab, and test them.

When lab tests consistently yield positive results, insecticide is then sprayed in the affected area. The spraying itself does two things:

1. Kill flying adult mosquitoes by spraying very small amounts of adulticides into the air. This spray is a fine mist that acts as a fogger.

2. Kill larvae by applying larvicides directly to the water where mosquito larvae have been detected. This helps kill more hard-to-reach areas.

People rightfully have many questions about whether these insecticides are safe for humans. They are safe because the dose and where they are applied are very purposeful. These insecticides work by overstimulating insect nerve cells until they’re paralyzed, but insect nerves are far more sensitive to the chemical than ours, and mosquitoes are tiny, cold-blooded, and can’t break the chemical down the way we can. So the same dose that’s fatal to them is far too small to hurt a person. How these insecticides are used also matters. Adulticide sprays are released as low-volume mist, and the droplets disperse and degrade quickly, resulting in very low human exposure. Larvicides are placed directly in standing water and target larvae through mosquito-specific biological mechanisms.

A 2025 review of community mosquito-control spraying found no causal relationship between adult mosquito-control applications and adverse human health impacts when applied appropriately, with estimated exposure levels far below regulatory concern.

People with asthma and other respiratory conditions are particularly concerned. But an older study in New York City found no increase in asthma visits, including among children, after West Nile spraying.

What this means for you: Reducing WNV is important, and spraying is safe. I’ll stay indoors during spraying when I can but won’t lose sleep over it. Check with your local public health or mosquito control department for the schedule—they’re supposed to publish one.

Good news

• More than 341,000 comments were submitted on the OMB’s proposed rule that could, quite literally, break science in the U.S. This is an enormous public response by any standard; public comment on federal rules almost never gets anywhere close to that volume. Way to show up for science discovery in the U.S.! Comments are now closed, and it’s time to see how the federal government responds.

Bottom line

From salad choices to mosquito bites to heat safety, this world just never gets boring. Stay healthy out there.

Love, YLE

Your Local Epidemiologist (YLE) comprises a team of experts, ranging from physicians to immunologists to epidemiologists to nutritionists, working together with one goal: to “translate” ever-evolving public health science so that people are well-equipped to make evidence-based decisions. The YLE suite of newsletters reaches over 475,000 people across more than 132 countries. This newsletter is free to everyone, thanks to the generous support of fellow YLE community members. To support the effort, subscribe or upgrade below:

Subscribe now

Some of this confusion is unavoidable, as outbreak investigations are messy and uncertain, unfolding quickly in real time. But some of it is a direct result of what happens when the glue holding public health together (i.e., the federal government) is simultaneously gutted, lacking transparency and centralized communication, and impacted by corporate interests.

So here’s what we know, what we don’t, and what it means for you.

What we know

• The culprit is a microscopic parasite called Cyclospora, which spreads through food or water contaminated with human feces. This parasite lives in the human gut and is shed in stool as a tough, thick-walled shell. This is why it survives on produce and resists rinsing and typical sanitizers.

• This outbreak, the largest in U.S. history, has topped 3,000 cases, and it’s not slowing down. That number comes from adding up state-level case counts, which are running well ahead of the counts on CDC’s website. For context, the U.S. typically sees around 3,000-4,000 cyclosporiasis cases in an entire year—so this single outbreak has already matched a normal year’s total, and it’s still climbing.

  • Note that the real number is almost certainly higher: most people with a few days of watery diarrhea ride it out at home rather than see a doctor, and those who do see a doctor may or may not get tested for cyclosporiasis (it’s an expensive test!).

• This outbreak is nationwide, with more than 31 states reporting cases. Michigan has the most cases—more than 1,600 confirmed—but that doesn’t mean it started there. It is more likely to mean Michigan is better resourced for testing, reporting, and epidemiological legwork, so more of its cases are getting caught and counted. Michigan cases continue to increase quickly.

• This outbreak is ballooning quickly because the U.S. hasn’t publicly pinpointed the contaminated food, not because it’s contagious person-to-person. When someone sheds the parasite in their stool, it isn’t immediately infectious—it needs 1 to 2 weeks in the environment to mature before it can make anyone else sick. Practically speaking, even without perfect hand hygiene, you’re not going to pass this to your family the way you would a typical stomach bug (called norovirus).

• Public health cuts have played a role here, but not the one getting the headlines. A lot of blame is landing on last year’s cuts to FoodNet, a CDC surveillance program. But FoodNet was never designed for real-time outbreak detection or response. Instead, it tracks longer-term background trends for research. The more accurate culprits are the lack of centralized coordination by the federal government, our siloed health systems, and insufficient capacity at state and local health departments. The work is laborious, and public health is chronically underresourced. Local public health departments are doing this while tracking everything else, like measles. If the American public wants a public health system, then the U.S. needs to pay for it.

• One chain has already pulled an ingredient: Taco Bell. And the number of entertaining tweets about this (Taco Bell leading the appropriate response to diarrhea) is not in short supply.

What we don’t know (with some educated hunches)

• Why is it taking so long to find a source? The only way to determine the cause is through epidemiological investigations (i.e., interviews with people to identify a common source) followed by lab testing. Interviews are particularly hard for cyclosporiasis because the person needs to recount food over the past 10 days. BUT, by now, hundreds of interviews have been completed, and there should already be signals from the noise. If there are signals about potential sources (which I’m hearing there may be), the information needs to be communicated (and quickly) at a national level. Regardless of whether there is a single definitive source or multiple potential ones, the longer the federal government takes to identify and name it, the more illness and hospitalizations we will see. It’s that simple.

• How did the contamination start? Still unclear. Broadly, there are two possibilities: contamination at the farm level (poor field sanitation, such as workers without adequate bathroom access, or contaminated irrigation water) or contamination during processing (typically via contaminated water at the packing or washing stage).

What this means for you

I know most of us would like to avoid having explosive diarrhea, but keep in mind that the risk is low (much lower than getting norovirus right now). Produce is healthy for you, and there are ways we can lower the risk without cutting it out completely.

This is how I’m thinking about it for my own family:

• Avoid the bagged or boxed salads for now, until there’s more clarity on which products and sources are affected. Whole heads of lettuce you wash and cut yourself are the safer bet in the meantime.

• Until a source is confirmed, lean toward produce with the least human handling. This means things you can peel, wash thoroughly, or cook. Produce with lots of bumps, grooves, and folds (leafy greens, berries) gives the parasite more places to hide, which makes it harder to wash off completely.

• Washing helps, but it won’t fully remove the parasite. Water removes some of it, but not all, because it clings and hides in nooks and crannies. Cooking will kill it, though I recognize “just cook your salad” isn’t a satisfying solution.

• If you are sick, be sure to talk to your clinical care team. Keep in mind:

  • Severe cases can be treated with antibiotics (called Bactrim). An older randomized controlled trial in Nepal showed that after treatment, parasites were detected in only 6% of patients (compared with 88% in the placebo group).

  • Symptoms can go away and come back for weeks. In one past outbreak, the longest case lasted 107 days. If your diarrhea keeps returning like this, it’s more likely cyclosporiasis than norovirus, so ask your doctor to test for it.

  • If a health department calls you for an investigation (i.e., interview), please participate. It will help others avoid the misery you’re experiencing and increase the likelihood of accountability down the road.

• Other questions I’m seeing:

  • Will you know if it’s on food because it smells like poop? No, these parasites are so small you won’t pick them up with smell.

  • Is this deadly? It hardly ever is. Most cases are mild, and severe cases can be treated. CDC is reporting 86 people hospitalized and no deaths.

  • If I’m old or pregnant, I’m already more worried, but is that warranted? Pregnant women, older adults, young kids, and anyone who is immunocompromised are more likely to get severely dehydrated or have a longer illness. Don’t tough out watery diarrhea. Call your clinical care team.

  • If I don’t go to the doctor, how is my data counted? It mostly isn’t. If you ride it out at home or your doctor doesn’t order that test, you’re not in the official count, which is a big reason officials think true case numbers are higher than reported.

  • Will a parasite cleanse work? No. The over-the-counter kits are typically some combination of herbal supplements and laxatives, and there's no evidence they clear Cyclospora or any other parasite.

Bottom line

This is a very large foodborne illness outbreak (a real shit show out there…), but there’s plenty we can do as individuals while we wait for government systems to catch up.

Now back to vacation. Be back next week with more!

Love, YLE

To get a deeper download, be sure to check out The Evidence Collective post yesterday.

A huge thanks to my friend and epidemiologist Dr. Caitlin Rivers over at Force of Infection for staying on top of the numbers and graphs so I didn’t have to while on vacation. Teamwork makes the dream work.

Your Local Epidemiologist (YLE) comprises a team of experts, ranging from physicians to immunologists to epidemiologists to nutritionists, working together with one goal: to “translate” ever-evolving public health science so that people are well-equipped to make evidence-based decisions. The YLE suite of newsletters reaches over 475,000 people across more than 132 countries. This newsletter is free to everyone, thanks to the generous support of fellow YLE community members. To support the effort, subscribe or upgrade below:

Subscribe now

Shirley was 70, recently widowed, and living alone in a home, with diabetes and high blood pressure. All winter, the boy next door would knock before a snowstorm to make sure she was okay. But checking tapered off as the weather warmed (which is typical, as more of us check on neighbors during extreme cold than heat). Once the first heat wave of the year came, she didn’t realize the extension cord powering her portable AC was unplugged. By the time anyone reached her, her body temperature had reached 107°F, and it was too late.

Heat is blanketing much of the country this week, and Shirley’s story will play out again and again. Just look to France: More than 1,000 excess deaths in just five days. But it’s not just deaths. Heat-related emergency room visits will also increase, along with other health problems, from heart attacks to pediatric asthma attacks. One heat wave will cost a state up to $900 million dollars.

During my time at CDC, I learned a lot about heat risk from the subject matter experts. Sure, the usual advice matters (stay cool, drink water), but there’s so much more nuance I wish every American knew as we adapt as humans.

So, here they are. Six hot tips you can use this week from a few of your local epidemiologists.

1. Don’t pay attention to just the temperature

120°F in Phoenix isn’t great, but 90°F in New York can be worse for your health.

You can see it in these maps from Dr. Joseph Allen. The left shows today’s temperatures (“not too bad”). The right shows the risk to your health (“it’s going to be very bad.”)

The reason is heat imbalance: Your risk depends not just on temperature but on humidity, air quality, wind, solar radiation, and how long you’re exposed. The danger is when your body makes more heat than it can release. Sweat is the main release valve: evaporating a teaspoon of sweat cools your whole bloodstream by about 2°F. But in humid air, sweat can’t evaporate, so your body can’t cool itself, and risk climbs fast.

So, instead of temperature in your weather app, watch two other metrics:

• Heat index is the “feels like” reading in your app. It combines air temperature with relative humidity to estimate how hot it actually feels to your body because when the air is already full of water vapor, sweat can’t evaporate as easily, so heat builds up. But, importantly, this assumes you’re in the shade and resting, not in direct sunlight, so it can underestimate risk.

• Wet temperatures are more precise because it’s literally a thermometer covered with a wet cloth, mimicking our body’s ability to cool itself with sweat.

Where do you go? The HeatRisk tool was developed just for this.

2. Medications matter

Heat is a double-whammy when it comes to medications:

1. Some medications, including over-the-counter drugs, can make you more sensitive to heat in many ways: reduce the sensation of thirst (e.g., ACE inhibitors); interfere with your body’s ability to regulate heat (e.g., antipsychotics); impair sweating and, thus, cooling (e.g., antidepressants); reduce the ability for blood vessels to dilate (e.g., aspirin); make it harder to sense when you’re overheating (e.g. opioid pain medications); and more. If you’re taking any of these, you must be extra careful.

2. Heat degrades or damages certain medications by altering the chemical make-up. This applies, for example, to insulin, EpiPens, and inhalers. Keep them in a cool place — and don’t leave them in your car.

3. Risk is not uniform

The risk of dying from heat illness depends a lot on where you live — and whether you have air conditioning or a cooling center nearby. In Sun Belt cities like Phoenix, 3 out of 4 heat deaths happen outside, mostly among homeless and outdoor workers.

In northern cities without universal AC, we worry more about people indoors. In New York City, most heat-stress deaths occur at home. In the 1995 Chicago heat wave, over 700 people died; most of them were older people living alone in apartments without AC. Without air conditioning, indoor temperatures can be much higher than outdoor temperatures, especially at night, and can remain elevated for days after a heat wave.

Beyond environmental factors, there are individual factors that increase risk:

• Pregnant women. There is strong evidence of heat impacting the rate of congenital heart defects, an increase in stillbirths, and more pre-term births.

• Kids with asthma. Heat can provoke asthma symptoms, especially because warmer temperatures can worsen air quality, and humidity can worsen lung function.

• People with cardiovascular disease. Extreme heat makes the heart pump faster and faster to get blood to our fingers and toes. While important, blood goes away from critical organs like the heart.

• Older adults. Aging blunts the heat response and reduces the ability to sweat, medications often impair regulation, and isolation means fewer check-ins.

• Pets get heat stroke too. Here are hot-weather safety tips for pets, including recognizing the signs of overheating, checking the sidewalk for hot pavement, and never leaving pets alone in cars.

4. What about fans? There is a bit of nuance here.

A fan cools you in one way and heats you in another. It speeds the evaporation of sweat, which is your body’s main cooling system, but once the air is hotter than your skin (around 95°F), it also blows heat onto you, like a convection oven. Which force wins depends on the humidity:

• In humid heat, sweat evaporates slowly on its own, so the fan’s evaporation boost matters a lot. It keeps helping well past 90°F.

• In hot, dry heat, sweat already evaporates fast, so there’s little left for the fan to add. The heat gain takes over, raising your core temperature and straining your heart.

This is why CDC and EPA guidance says to stop using a fan once indoor temperatures pass 90°F (or the heat index passes 99°F). It’s a good rule of thumb, but it’s also really time to go to a cooling center: a library, mall, museum, or any public building with AC.

5. By the time you feel thirsty, you’re already behind.

Dehydration is a common driver of heat illness. But thirst doesn’t kick in until you’ve lost about 1–2% of your body weight in fluids. In older adults, that signal arrives even later.

• Drink before you’re thirsty. Aim for about 10 cups of water throughout the day, and more on hot days.

• If you’re working or exercising outdoors, target about 8 ounces every 20 minutes.

• Water is usually enough, but if you’re sweating heavily for more than an hour, you lose sodium and other electrolytes along with water. Replacing fluid losses with only plain water can dilute your system, which creates additional problems.

• Watch what you drink. Remember, alcohol works against hydration. Caffeine, despite its reputation, has largely been cleared. Moderate amounts won’t meaningfully dehydrate you.

6. The signs of heat exhaustion and heat stroke are different

Heat-related illness happens on a spectrum. It can start mildly with a headache, then progress to heat exhaustion, which can progress to heat stroke, a medical emergency. Knowing where someone falls on the spectrum tells you whether to cool them down at home or call 911 right now.

This matters a lot in rural areas, especially when the nearest ER is an hour away, and EMS takes far longer to arrive. The first response often falls to family, coworkers, or whoever happens to be there.

Bottom line

It’s going to be a hot summer, and we are going to need to start adapting to extreme heat more and more. But the best tool is still each other. Stay cool out there and go check on your neighbor, like Shirley.

Love, YLE MD and MW

Your Local Epidemiologist (YLE) comprises a team of experts, ranging from physicians to immunologists to epidemiologists to nutritionists, working together with one goal: to “translate” ever-evolving public health science so that people are well-equipped to make evidence-based decisions. The YLE suite of newsletters reaches over 475,000 people across more than 132 countries. This newsletter is free to everyone, thanks to the generous support of fellow YLE community members. To support the effort, subscribe or upgrade below:

Subscribe now

A military flu outbreak continues to increase after the removal of a vaccine requirement. A summer flu outbreak? Yes, it’s possible, and yes, it sure feels like we’re spending an awful lot of energy undoing lessons earlier generations learned the hard way, only to reinstate them once we've relearned why they existed.

We’ll close with some good news and a question from the YLE community: Does DEET attract mosquitoes?

Here’s what’s going on, and, most importantly, what it means for you.

Disease weather report

Heat risk rises

Large swaths of the U.S. will be dangerously hot this week, on the heels of an extreme heat wave in France that led to 1,000 excess deaths across 5 days. The risk in the U.S. peaks Thursday, when more than 170 million people will be in areas at “high” or “extreme” health risk from heat.

What this means for you: If you live in the red or purple patches above, everyone needs to take action, not just those who are high-risk. Enter your zip code for guidance. YLE will be back tomorrow with more tips and tricks.

Very small signs of Covid-19?

Every summer, the U.S. sees a Covid-19 wave, and this year should be no different, though the big question is how large it will get. Each year’s summer wave has been smaller than the last, and I hope it eventually becomes a blip.

Nationally, wastewater levels are extremely low, among the lowest we’ve seen in a very long time. But movement is starting in Southern states, and emergency department visits there, while still low, are beginning to climb. This is typically where the summer waves begin.

Spotlight: Military flu outbreak follows a vaccine requirement policy change

You’ll notice the flu didn’t appear in the disease weather report above. Yet a flu outbreak has hit the military just weeks after a policy change made vaccination optional for active-duty service members. Nearly 300 at a boot camp are now sick.

How is a flu outbreak during summer possible? And is it truly because of the policy change?

What is unfolding at these training camps is essentially a combination of bad luck after a risky policy:

1. Flu never disappears. A big June outbreak is unusual, but flu doesn't vanish in summer; it just drops to very low levels. Wastewater for Flu A is essentially zero right now, with only sporadic Flu B. But a spark is possible.

2. Once it sparks, the environment plays a big role. And this is a unique environment. Spread comes down to a few things: environment (human behavior), weather (cold, dry air), and the usual unknowns. Recruits live, eat, sleep, and train in tight quarters around the clock, so even with summer weather working against it, the virus has room to move. Epidemiologists have watched flu burn through summer-camp dorms for exactly this reason. Wider community spread is unlikely, though: the weather is wrong, school is out (students are a major driver of transmission), and recruits confined to base have little outside contact.

3. Policy impacts behavior. The general public doesn’t get vaccinated this time of year, since there’s generally not much flu to vaccinate against. But basic training is the exception: according to veterans, recruits are vaccinated on arrival, regardless of the month. After the requirement was dropped, only about 40% of new recruits chose the shot, down from near-universal coverage before (roughly 99% in the Navy, Air Force, and Marines, and about 98% in the Army). We don’t know whether this outbreak was caused by the same flu strains the vaccine covers.

Dropping the flu vaccination requirements is a scientifically and economically risky decision. The requirement had been in place since the 1950s for one simple reason: military readiness depends on keeping troops healthy and in the field. Remember, the Spanish flu took as many American lives in the barracks as battle did in WWI.

So, did this outbreak dent readiness? This is important because it’s one of the rationales for a requirement. This is where a denominator would help, and I haven’t found one reported publicly. Three hundred sick out of 400 means basically the whole base went down, which is bad for preparedness. The same 300 out of 6,000 is under 3%, which seems more manageable.

The vaccine requirement was quietly reinstated last week. This is the right call, as this outbreak foreshadows the possibility of an outbreak affecting all troops during the actual flu season. That certainly would impact military readiness.

As epidemiologists say: Bugs have ears.

Good news

• Medicare gets access to reduced-price GLP-1s. Starting Wednesday, some Medicare recipients will be able to get the drugs for a $50-a-month co-payment. Here are the criteria. The coverage is only for a temporary trial period, set to expire at the end of 2027.

• Naloxone options expand. The FDA approved another over-the-counter nasal naloxone. More options on the shelf mean more competition, lower prices, and easier access to a medication that can reverse an opioid overdose in minutes. Wider availability saves lives.

• A new mRNA flu vaccine. Remember that flu vaccine that RFK Jr.’s FDA said they wouldn’t review and then, after immense backlash, reviewed again? Well, we got exciting news: the external FDA advisory panel voted 9-0 to back Moderna’s mFlusiva (mRNA-1010), set to be the first mRNA-based seasonal flu vaccine in the U.S. In a trial of over 40,000 adults aged 50 and older, it cut symptomatic flu by about 27% compared with a standard shot, with a bigger effect on hospitalizations and immune responses than even the high-dose senior vaccine. With a final FDA decision expected by August 5, it could be available for the 2026–2027 season.

  • But there’s a major wrinkle. The U.S. has no functioning ACIP, due to ongoing legal battles between the American Academy of Pediatrics and RFK Jr. So while the FDA may call it safe and effective, no one is in place to set policy on who gets it and when. That likely means Americans won’t have access to this vaccine this fall, but it’s worth following closely.

Question grab bag

Any truth to the study that DEET might attract mosquitoes?

There is no evidence DEET intrinsically attracts mosquitoes. A recent 2026 lab study showed that they can be conditioned to associate fading DEET with food, prompting many headlines. This associative learning from mosquitoes is fascinating, but the number of times a mosquito feeds over its natural lifespan is in the single digits (3-5ish, depending on species). There has also been some research suggesting that a single mosquito species may become somewhat desensitized to it over time.

The practical takeaway remains the same, though: keep using DEET and reapply regularly. It remains one of the most effective preventive measures we have against mosquitoes, and we are enterinig mosquito-borne illness season.

—Dr. Marisa Donnelly, YLE NY correspondent, trained in mosquito-borne illnesses.

Bottom line

Heat is the immediate health threat this week, so start there (check your zip code). But the bigger takeaway is that the public’s health suffers when systems quietly stop doing the boring things that keep us safe.

Love, YLE

Your Local Epidemiologist (YLE) comprises a team of experts, ranging from physicians to immunologists to epidemiologists to nutritionists, working together with one goal: to “translate” ever-evolving public health science so that people are well-equipped to make evidence-based decisions. The YLE suite of newsletters reaches over 475,000 people across more than 132 countries. This newsletter is free to everyone, thanks to the generous support of fellow YLE community members. To support the effort, subscribe or upgrade below:

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CDC and HHS are calling the containment a success. And it is. A lot of unglamorous work went into keeping it small—with WHO leadership from the beginning; experts in global migration, rodent-borne disease, and special pathogens who understand this virus; the biocontainment teams in Omaha; the local and state health departments doing the daily monitoring.

But one thing also can’t be ignored: the Administration’s response was dripping with absolute, extreme irony.

American citizens were ordered to be held in a federal facility against their will after CDC’s own medical reviewer and other outside experts recommended they be allowed to be monitored at home. The orders were signed by Jay Bhattacharya as acting CDC director. This is the same guy who built a public profile arguing that the Covid-19 response went too far against medical freedom, now taking away more freedom from U.S. citizens than CDC scientists deemed necessary. (And an Administration that continues to discredit, undermine, and disparage scientists working during the Covid-19 response.) Eventually, after pushback from public health and states, the White House and HHS let the cruise ship passengers go quarantine at home, but also suggested extreme conditions, such as wearing ankle monitors.

Talking about plans (and criticizing other people’s plans) is easy; actually implementing plans in a real-world health emergency is much harder.

Now that it’s happening with Covid-19 contrarians, does this mean we can finally have an honest national reckoning? Can we finally have a serious conversation about the role of non-pharmacological interventions like social distancing, contact tracing, and masking, the trade-offs, where authority lies, and… humility?

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But what if we could eliminate one cancer?

After 40 years of slow progress, it’s starting to happen with cervical cancer. It could become the first cancer we drive from a major public health threat down to something rare—what the WHO calls elimination, fewer than four cases per 100,000 women.

Last week, the world got the news that, between 2020-2024, researchers could not find one woman aged 20–24 who died of cervical cancer in England. A finding like this has never happened before.

Here are five reasons this news is miraculously hopeful, and why it still comes down to us.

1. We finally have proof at the bar that matters most

The cervical cancer story began with Harald zur Hausen’s then-radical 1980s claim: a virus (not lifestyle) causes cervical cancer. This prompted researchers to design a vaccine. It won him a Nobel Prize.

For decades, the vaccine trials could only measure persistent human papillomavirus (HPV) infection and pre-cancer, because cancer itself takes decades to develop. But it was highly effective against these markers. As soon as we learned this, it would have been indefensible to keep a placebo group from receiving the vaccine for decades in order to measure the vaccine’s impact on cancer. But the lack of a trial to demonstrate a direct effect on mortality led to doubt, falsehoods, and rumors among some.

Now the evidence is in: the HPV vaccine prevents mortality. And thankfully, we didn’t delay a placebo group all these years, as it would have resulted in millions of preventable deaths worldwide.

2. This virus hands us a winnable fight

Most cancers are caused by a tangle of genes, environment, age, and bad luck. Cervical cancer is the rare exception because nearly all cases (99%) trace back to one thing: persistent infection with high-risk strains of HPV.

That single-cause structure is what makes elimination thinkable at all. Block the virus and you block the cancer, years before it could ever start. And because HPV is so common—roughly 80% of unvaccinated people will catch it at some point—vaccinating an entire generation also starves the virus of hosts, protecting even people who weren’t vaccinated.

3. Evidence holds up from every angle

A claim this big has to survive every challenge. This one does.

1. “Increased survival is from screening rather than the vaccine.” Screening does save lives. However, in 2004, England raised the routine screening age by five years, from age 20 to age 25, thereby reducing screening among young women. The study found zero deaths anyway.

2. “It’s a statistical fluke.” There truly were zero cases of cervical cancer in this group, but researchers noted not to expect zero cases every year because of statistical uncertainty. Regardless, the “worst case” scenario is an 85% reduction in mortality. The vaccine’s impact is not a statistical fluke.

3. “It’s just less sex.” If changes in sexual behavior could explain away these findings and it were true people were having less sex, one would expect that other sexually transmitted infections would also be disappearing. However, as the researchers point out, England at this time saw only modest changes in other STIs in this exact age group.

4. One dose may be all it takes

For years, the vaccine was given in two or three doses. But mounting evidence, now spanning trials and long-term follow-up across multiple countries, shows that a single dose provides protection comparable to multi-dose schedules for cervical cancer. (For other HPV-related cancers, maybe, but we need more data.)

The evidence is so compelling that WHO has now endorsed single-dose schedules partly for these reasons, and several countries have switched. The hardest part of HPV vaccination has been getting adolescents, especially in the countries that bear most of the cervical cancer burden, to come back for repeat visits. A one-shot schedule with comparable effectiveness eases access and makes eliminating cervical cancer a real possibility for many countries.

5. What we’ve seen is a fraction of what’s coming

This study modeled that about 23 deaths should have occurred in that youngest group, and across all young women, the program has already prevented close to 200 cervical cancer deaths in England. This seems small, but what we are seeing is the leading edge of a wave that builds for decades. Cervical cancer rarely strikes women in their early 20s; the disease takes decades to develop and normally peaks in a woman’s 30s, 40s, and 50s.

This is also bigger than cervical cancer. HPV drives cancers of the throat, anus, and elsewhere—and HPV-related throat cancers are rising, particularly in men. That’s why vaccination now includes boys, too. The fact that one virus causes nearly all cases of cervical cancer is exactly what makes it so beatable.

Now comes the hard part

Equally important to celebrating progress is realizing that the hard work is not done. Having a vaccine does not mean everyone gets vaccinated.

England reached this milestone on roughly 90% uptake. As of 2024, 79% of adolescent girls and 77% of boys in the U.S. have received at least one dose. This seems high (it is high), but those numbers hide enormous gaps. For example, adolescent girls with at least one dose range from 85% in Massachusetts to 57% in Mississippi. Adolescents living in rural areas, uninsured children, and those from lower-income families are all vaccinated at significantly lower rates. The HPV vaccine can only eliminate cancer for these individuals if it reaches them.

Vaccine hesitancy is rising, and the policy environment is unstable. Communities with the lowest vaccination rates often have the least access to professionals who build confidence to vaccinate and catch cervical cancer early. This is a problem that compounds without action.

If you are a parent or have kids or adolescents in your life, ask about the HPV vaccine. If you work in health care, remember your recommendation remains the most important predictor of vaccine acceptance. And if you live in a community with low uptake, advocate for better access, talk to your leaders and policymakers to ensure everyone has the opportunity to be vaccinated.

Bottom line

Cancer finds everyone, whether directly or through a loved one. But now, for cervical cancer, it doesn’t have to. This is a huge win for women’s health, with extraordinary potential. But it still comes down to us.

Love, YLE and DH

David Higgins, MD, MPH, is a practicing pediatrician and public health physician whose work focuses on vaccine delivery, health policy, and communication. He publishes the newsletter Community Immunity, where he writes about vaccines and public health. When he’s not seeing patients or writing, he’s coaching youth soccer or exploring the outdoors with his family. Find him on LinkedIn and Instagram.

Your Local Epidemiologist (YLE) comprises a team of experts, ranging from physicians to immunologists to epidemiologists to nutritionists, working together with one goal: to “translate” ever-evolving public health science so that people are well-equipped to make evidence-based decisions. YLE suite of newsletters reaches over 475,000 people across more than 132 countries. This newsletter is free to everyone, thanks to the generous support of fellow YLE community members. To support the effort, subscribe or upgrade below:

Subscribe now

Last night, I had a choice: write a YLE post or watch the sunset with my young daughters and popsicles. I picked the sunset.

So, no post today—I’ll be back Wednesday. In the meantime, here’s a picture I snapped of the beautiful, peaceful moment with them.

Summer is here. And a very happy, belated Father’s Day to the best and most involved generation of dads in recorded history. (Please come home soon.)

Love, YLE

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Most online rumors or falsehoods do their damage slowly: polarization, eroded trust, and fractured public discourse. But there is one corner of the landscape where the consequences are immediate, and far easier to measure: cancer. That matters enormously for patients themselves, but it also gives us the clearest case study of why bad health information spreads so well—and what actually stops it.

Why cancer is uniquely vulnerable

A cancer treatment decision is about as high-consequence as a health decision gets, but features of the disease make it unusually prone to a confusing and ultimately dangerous information environment:

1. Cancer is extraordinarily complex. The word covers hundreds of distinct diseases and thousands of treatment options, and clinical practice guidelines grew exponentially in length between 1996 and 2019. In addition, what causes cancer is a complex combination of genetics, environment, and chance. This complexity is fertile ground for confident, simple-sounding answers.

2. Most cruelly, the diagnosis itself disarms the patient. Psychological distress, fatigue, and information overload are common and can cloud cognitive reserves. The patients who most need to make careful decisions are overburdened when it’s time to decide.

3. Recommended treatments often have terrible and sometimes lifelong side effects. Alternatives to surgeries, hair loss, nausea, fatigue, weight change and other serious side effects can certainly sound appealing. Cancer patients are in a desperate catch-22 between cancer and awful treatments.

4. There’s money in exploiting it. The U.S. alternative medicine industry was estimated at $30 billion in 2022. This creates strong economic motives to target desperate patients with familiar-sounding, out-of-pocket “cures” like high-dose vitamins, supplements, or rigid diets.

And the exposure to falsehoods isn’t limited to people who already have cancer. Screening and vaccination are decisions healthy people make (in the same noisy environment, often with less urgency to get them right), so the vulnerability starts well before any diagnosis.

Falsehoods and rumors take advantage of this environment and cause measurable harm. Cancer is a model topic for studying falsehoods and rumors precisely because its consequences are so measurable. Unlike political misinformation, where real-world effects are diffuse and harder to trace, cancer falsehoods produce outcomes we can track more directly: treatment adherence, survival rates, mortality.

A 2018 study found that cancer patients who chose alternative treatments over conventional ones were more than twice as likely to die within five years. For colorectal and breast cancer, the risk was 4.5 and 5.6 times greater (or a 350% and 460% increase in the risk of death, respectively). That matters because cancer is the second leading cause of death, and 40% of people will be diagnosed in their lifetime.

The algorithm and identity challenge

Across YouTube, TikTok, Instagram, and Twitter, low-quality content gets more views, more likes, and more shares than accurate content. A 2024 review documented just how thoroughly falsehoods have saturated the cancer information environment. One study found that inaccurate cancer articles were 28 times more likely to be shared than factual ones. The reason is structural: algorithms reward engagement, and fear, hope, and outrage drive engagement far more reliably than careful, evidence-based communication.

But flooding the zone with better information fails, and for a deeper reason: identity. Once a belief attaches to an important social identity (an anti-establishment worldview, distrust of pharma, a community of fellow patients seeking alternatives), challenging it stops feeling like a factual dispute and starts feeling like a personal attack. People dig in.

A diagnosis is itself a profound identity disruption, and alternative treatment communities offer something oncology waiting rooms often cannot: belonging, agency, and hope. The social and psychological rewards of those communities are real, even when the medical claims are false.

A new study shows the mechanism in real time. After a viral podcast episode in which celebrities promoted ivermectin and fenbendazole as off-label cancer treatments, prescribing rates doubled overall and rose more than 2.5 times among cancer patients specifically, across nearly 70 million patient records nationwide. The sharpest increases were among white patients, men, and Southern residents, mirroring the demographic profile of the platforms promoting the claims. Causality is hard to parse here. We cannot say whether the podcast drove the prescriptions or tracked an online conversation already growing. But, the falsehoods didn’t spread randomly. They traveled through identity-aligned networks already primed to receive it. The same communities that promoted ivermectin for Covid-19 later promoted it for cancer. The claim changed; the underlying identity orientation did not.

The same dynamic shapes prevention falsehoods, too. Vaccine-skeptical networks spread HPV vaccine claims through the same identity-based channels, even if the specific communities involved are different.

What would actually help

Cancer rumors are a textbook case of false empowerment: compelling precisely because they speak to people living in fear. There’s no single fix, but the research points to a few things:

1. Train clinical care teams to address falsehoods. Just 18% of physicians report any formal training in addressing unproven treatments, even though 99% of oncology practitioners encounter it regularly. Care teams need the communication skills to correct falsehoods and do so without making the patient feel attacked. The goal is to connect with what the patient values first, then address the belief.

2. Prebunk before patients go searching. Don’t wait for a bad claim to return to the exam room. Warn patients or family members in advance about what cancer myths look like, and give them one simple tell: if someone is selling you a cure, be skeptical. Clinics offering unproven treatments spent an estimated $15.8 million on Google Ads targeting cancer patients’ search queries between 2012 and 2023. A short heads-up beforehand beats a correction afterward.

3. Empower patients, do not just correct them. Alternative communities offer belonging, agency, and hope. Instead of only stripping out the false version, supply the real one: a trusted relationship and the skills to evaluate what patients find on their own. Strong health and media literacy skills, along with high trust in science, are among the most consistent protections against health falsehoods. Give people agency and a trusted place to bring their questions.

4. Support the infrastructure around trusted messengers. We do not fix a fractured information environment by broadcasting more facts into the noise alone. The trusted messengers (the doctor who listens before prescribing, the community figure who knows the family) work because they are in a relationship with the people they serve. But asking trusted messengers to show up and respond to myths and bad information only works if we support them. Many want to, but they run into real barriers: insufficient training, lack of time, online harassment, and limited institutional support. The fix is engagement training plus institutional backing that provides resources and infrastructure to do so.

5. Meet people where they are. It’s important to be present on social media, podcasts, and other digital platforms where patients often seek answers. Corrections from credible experts do reduce false beliefs, and the people quietly watching the exchange are often the ones who update. Even publishing in more traditional venues, such as university websites and major newspapers, has real value. AI companies are paying to train on high-quality journalism, and AI search tools disproportionately rely on authoritative institutional sources, especially for health questions.

We can also direct patients to evidence-based complementary approaches that may help them feel empowered alongside conventional treatment, as well as support them physiologically.

Bottom line

Cancer falsehoods online are directly linked to higher rates of death, yet we still treat them as something for individual patients to navigate and individual doctors to address in brief appointments, while platforms continue doing the opposite. It’s the clearest example of a lesson that reaches far beyond health: when trust breaks down, misinformation need not be convincing; it only needs to be available. Building resilience means creating the social conditions where trusted people shape our most important decisions.

Sincerely, MF

Big thank you to Dr. Andrea Betts, a cancer researcher expert, for her input and edits on this post.

Dr. Matthew Facciani is a social scientist and researcher at the Yale School of Public Health who studies why people believe what they believe. He is the author of the award-winning book Misguided and creator of its companion podcast, newsletter, and media literacy tools, all designed to help people navigate today’s complex information landscape.

Your Local Epidemiologist (YLE) comprises a team of experts, ranging from physicians to immunologists to epidemiologists to nutritionists, working together with one goal: to “Translate” ever-evolving public health science so that people are well-equipped to make evidence-based decisions. YLE suite of newsletters reaches over 475,000 people across more than 132 countries. This newsletter is free to everyone, thanks to the generous support of fellow YLE community members. To support the effort, subscribe or upgrade below:

Subscribe now

Speaking of shared joy, the World Cup has officially kicked off, and we are here with what the health data show. We’re also at peak tick season, and mosquitoes and infant botulism have entered the chat. Other low-risk but high-consequence things are happening, including bird flu heating up among cows again.

And pediatricians are getting bombarded with vaccine questions. We answer the latest and update a resource for you.

Here’s what’s going on and, most importantly, what it means for you.

Disease “weather” report

We are at peak tick season

Across much of the U.S., we’re in the heart of tick season. After starting earlier than usual, it’s now tracking close to previous years. I’m hopeful we’ll see activity taper off over the coming weeks.

What this means for you: It’s still important to enjoy the outdoors, so prevention is the name of the game. Use an EPA-approved repellent, wear long pants when possible, and do a quick tick check afterward. The vast majority of ticks don’t carry diseases, but regardless, the sooner a tick is removed, the lower the risk of transmission.

Mosquito season is here

Mosquito season is ramping up across much of the country. We can expect mosquito-borne diseases to peak in August or September.

Why? Mosquitos are cold-blooded, so transmission is a bit like a chemistry experiment. If it’s too cold (below ~16°C or ~60°F), the mosquito life cycle slows down too much to spread disease. Closer to the “magic temperature” of ~25°C / ~77°F, mosquitoes are happier and diseases spread a little more easily from mosquito to human.

West Nile is the leading cause of mosquito-borne disease in the U.S. It is a fairly new disease—25 years ago, we didn’t have it around. But it is very rare. So far this year, we’ve seen only 13 cases of West Nile. (In June 2025, we had 62 total and August had the most cases at 958)

What this means for you: Your risk depends on geography and other factors, including older age. As mosquito populations grow, it’s worth dusting off the bug spray and clearing standing water around your home.

Low risk to you, but disease of high (and potentially) consequence

Several outbreaks are on my radar, but all remain very low risk to the general U.S. public:

• Another infant botulism outbreak tied to baby formula. Nara Organics has recalled its organic formula, sold nationwide at Target, after three babies between 2 and 5 months became critically ill in CA, PA, and WA. Like the ByHeart recall last fall, it’s a niche product (under 1% of supply). What makes this one sting a little more: ByHeart had actually pointed parents to Nara as the safe alternative after their own recall. Regardless, it’s a reminder of how much we depend on the systems around us working.

• Ebola cases in Africa have climbed to 808, including one of the largest single-day jumps over the weekend. The cumulative total has already surpassed what the two biggest prior outbreaks reached at the same point in their first 100 days. This is a sign this one is likely to grow very large. If you're traveling to Africa (or have patients traveling), check out the YLE decision tree here.

• Bird flu (H5N1). After months of relative quiet, the USDA reports a sharp jump in infected dairy herds: in the past 30 days, 45 tested positive in Idaho, 2 in Utah, and 1 in Texas. We’re not at 2024 levels, but this is more than we’ve seen in a while.

Healthy Cup

The World Cup has officially begun, and the good news is that there have been no significant health events so far. Overall health risks remain low, but we’re watching three signals:

1. Heat. On opening day, Fan Fests in the Texas area saw nearly 100 fans fall ill from the heat, some requiring hospitalization. This is concerning because for every reported heat illness, many more sit just short of emergency, like dehydration and falls, cardiac problems, kidney stress, and mental status changes in elders. The “count” (22 out of ~30,000 attendees) underestimates the harm. Keep cool; drink water; know that alcohol and drugs mask heat injury symptoms, and common medications increase heat vulnerability. Go here to see your heat risk this week.

2. Measles. A few outbreaks are happening in the background, but two “sparks” sit particularly close to World Cup events, and we need to ensure they don't turn into wildfires:

   1. Wastewater monitoring has detected a signal in Chester City, Delaware County (15 miles from Philadelphia Stadium).

   2. One case among an unvaccinated resident in Santa Clara County, California, with recent international travel and community exposure, including at the airport.

3. What other things are people worried about? The YLE weekly survey of World Cup goers started last week. No major health rumors are surfacing yet (only 13% have heard any), but there’s concern about traffic and transportation accidents, as well as ICE.

Good news

We can always use it. Three today:

• FDA clears a screwworm treatment for dogs and cats. The FDA authorized emergency use of generic nitenpyram tablets for infected pets, expected to kill most larvae within hours. New World screwworm numbers continue to climb, with 12 animal cases across 7 counties. This medication is not preventative but an important new tool if an infection occurs—and more will be happening given how quickly this thing spreads.

• A new sunscreen ingredient, the first in over two decades. The FDA has approved bemotrizinol, used for years in Europe, Asia, and Australia, where it’s prized for strong, stable protection against both UVA and UVB. The approval spotlights a U.S. quirk: because sunscreens are regulated as drugs here, new ingredients can take years or decades to reach consumers. Products could appear later this year, though wide availability will take time. Read more about sunscreen at the YLE deep dive here.

• A lab-grown heart-muscle patch. Researchers implanted a stem cell-derived patch of heart muscle onto the failing hearts of 16 patients with advanced heart failure. The effect was real but modest, more of a signal of progress. Read more here.

Question grab bag

“This week I have encountered several patients saying “vaccines are only studied for 5 days.” Can you update your 12 questions about vaccines handout to address this succinctly? It would be very much appreciated. - A tired pediatrician.”

This is a common rumor. That figure comes from a line in the package insert describing the short window when vaccine trial participants fill out a daily diary card (see below for an example). But that card is only tracking the expected, short-lived reactions to a vaccine (sore arm, redness, fever, fussiness), which are caused by the immune response itself and reliably fade within a few days. Symptoms that persist longer usually point to a different cause, like an unrelated infection picked up around the same time, so that brief window is all the diary card needs to cover.

But vaccine monitoring doesn’t stop there. The same trials track other health events for months to years, recorded as they happen rather than on a checklist. And for routine childhood vaccines, those original trials are now just the starting point: we have real-world safety data on hundreds of millions of children across decades, consistently showing that the benefits far outweigh the risks.

We’ve updated the FAQs for paid subscribers, with the latest is available below. Thank you for all your effort, and all clinical care teams on the front line.

Read more

That system is now under direct threat.

The Office of Management and Budget (OMB) has proposed a new rule to regulate all federal grants, not just science, but housing, education, defense, NASA and everything in between, that would fundamentally change how research is conducted in the United States.

There have been a lot of fires in the past 16 months, and if everything is an emergency, nothing is an emergency. But this is a very big deal. These rules would strip away the independence that has kept science from becoming a political tool.

The good news is there’s still something we can all do.

How the grant system was designed to work

When I was a new faculty member, I was full of millions of ideas, so I sat down and wrote an NIH proposal. I worked on it for months and thought it was so good. Then I sent it to my mentor.

It came back covered in comments. Places where my reasoning wasn’t as airtight as I’d thought, methods that could be stronger, gaps in my thinking that I had been too close to the work to see. It stung, as honest feedback always does, but peer review almost always makes the work better. In fact, it’s the backbone of how American science has functioned for generations.

At NIH, submitted proposals go to a panel of scientists who have experience in the field. These are the people who can read research methods and spot their weaknesses, who understand when an experiment is designed well and when it isn’t. Applications are scored rigorously, and often only the top 3-20% of proposals receive funding. The people making funding decisions are required to justify them based on these reviews.

To be clear: this is not a perfect system, and good science still goes unfunded more often than any of us would like due to limited resources. There is also criticism that peer review may undervalue bold ideas that are risky but could have high payoffs.

But the peer review system is nonetheless a meaningful part of the grant selection process. While thoughtful and careful changes could improve the system, the changes being proposed by OMB will not make things better.

The rule that could change everything

Through this OMB proposal, the system that helps decide what gets funded is being dismantled.

There are many troubling elements buried in this proposal, but three provisions stand out in particular. Each would be damaging alone. Together, they would change what kind of science gets done in America, and who it serves.

1. Political appointees would decide which science gets funded, and peer review would be explicitly sidelined or ignored.

The guidelines your doctor follows, the standards that determine what’s in your air and water, the drugs that get approved for your family: all of it starts with a funding decision. Right now, that decision is made by scientists who can evaluate whether the work is actually sound and whether it could move the needle forward. Under this proposal, funding decisions could be made by political appointees.

The careful, expertise-driven review process that shapes grant funding would be effectively sidelined. That means that a poorly designed study could get funded simply because someone in a political office liked the sound of it, while rigorous, important work doesn’t get funded because it no longer aligns with the administration’s priorities. In other words, critical work that benefits all of us could now be missed just because it has become politically inconvenient.

2. Grants could be canceled at any point, without warning, in the middle of ongoing work.

Say your tax dollars have been paying for a cancer study for two years. The grant was awarded for five years, so the team is mid-experiment. There are three additional years’ worth of answers that could change how the disease is treated for hundreds of thousands of people. With this new rule, the federal government could cancel the remaining funding tomorrow, walk away from the commitment it made with your money, and have no legal obligation to finish what it started.

This is a huge waste of money. There are rarely other sources of funding for this work, which means the team, the graduate students, postdocs, and research staff who have dedicated years of their careers to this project could lose their jobs. Patients who have contributed their time to studies may not see it turn into useful learnings for others. Every hour of work already completed could result in nothing useful.

Science can take decades to get to tangible outcomes. It needs a stable funding system to flourish.

3. Researchers would have a harder time communicating their findings without pre-approval from the federal government.

There is a saying from Sir Mark Walport: “Science isn’t finished until it’s communicated.” Science is no use to anyone if it is kept locked away in the labs that produced the data.

The proposed rule could make communicating research findings harder in a number of ways:

• Make it harder for scientists to widely share their findings in scientific journals. Publication costs, including journal fees that allow for broad public access, could not be paid for by federal funds which is often how scientists pay these costs.

• Restrict researchers from engaging publicly about how their findings should inform policy or public health guidelines. This would restrict scientists from doing the work that transforms years of lab work into decisions that actually affect people’s lives.

• Make it harder for scientists to attend conferences. Conferences would now need to be approved by the federal agency at the time of grant award. This disadvantages conferences or publications that are not politically aligned. Conferences are a key way in which scientists learn about work happening in their field so they can collaborate and build on each other’s findings.

What good is science with a muzzle?

The long-term impact

These changes could (and hopefully would) be reversed under the next administration. But by then, damage has been done. Once projects are halted or denied funding by political appointees, people leave their science careers for other paths or even leave the country to do their amazing science elsewhere.

You cannot pause a scientific study the way you pause a subscription you decided isn’t useful anymore. You cannot freeze a research team that depends on salaries to feed their families, causing a scramble for replacement funding that, in most cases, simply does not exist. When the money stops, everything stops, and all the work in progress and its potential are lost.

Despite all of the language about reducing waste, fraud, and abuse, this new proposed rule increases the administrative burden tremendously.

Every researcher watching this unfold will make a rational decision: don’t start anything that will take a decade to finish. This includes not building a team around funding that could vanish, or asking the big questions that need patience and stability to answer. The most consequential science, the kind that produces the treatments and the breakthroughs that reach your doctor’s office twenty years from now, is exactly the science that would be abandoned first.

This is still a proposal, so we can all do something

Some worry this rule is already a done deal. But by law, OMB is required to open a public comment period. Those comments matter because they inform members of Congress, they can be used in litigation, and they create a public record.

So here’s what you can do:

1. Submit a public comment. The public comment period on this proposed change is open until July 13. Anyone can submit a comment, and OMB is required to respond to substantial ones. Each comment must be different to count as distinct; identical comments will be counted only once. Comment as an individual, not on behalf of your organization. Here’s a full resource to help you, with useful examples, but in general:

   1. Share a story about how science or federal funding has benefitted you or is involved in your work. Are you or someone you loved a cancer survivor? Do you know someone with Alzheimer’s? Have you received NIH/NSF or other federal funding? All of these can be stories you use to highlight why you care.

   2. Explain why you’re worried about these proposed changes. You can use the wording found here or in other resources to help you.

   3. Ask them to withdraw this proposed rule.

2. Contact your elected representatives. Congress allocates money to federal agencies to spend, and it has oversight of how that process works. You can let your representatives know this proposed change concerns you and ask them to intervene. There are levers they can push that can help at this moment.

3. Let others know why federal funding matters. This isn’t just about science, but ALL federal grants, including for education systems, defense projects, and more. The process, including the importance of federal funding, is invisible to many. We can all make it more visible by sharing how science benefits us and why we value it. You can also share this article, or any of the resources linked here, to help spread awareness!

Bottom line

We are quickly losing ground in scientific research in the U.S. More changes, like the proposed rule by OMB, would decimate our ability to conduct research here, leaving us all worse off: fewer treatments for pancreatic cancer, less research on pollution impacts, fewer answers for patients with rare disease, and more unaddressed health needs. The impact will be very real for all of us, regardless of where we stand politically.

Using our voices for science is more important than ever.

Love, LM

Big thanks to Dr. Megan Ranney for reading this over and providing brilliant insights, as always.

Dr. Liz Marnik, PhD, is Executive Director of The Evidence Collective at YLE and a science communicator and immunologist working at the intersection of public trust, science, and public health. You can find her on Substack, LinkedIn, Instagram and Threads.

Your Local Epidemiologist (YLE) comprises a team of experts, ranging from physicians to immunologists to epidemiologists to nutritionists, working together with one goal: to “Translate” ever-evolving public health science so that people are well-equipped to make evidence-based decisions. The YLE suite of newsletters reaches over 475,000 people across more than 132 countries. This newsletter is free to everyone, thanks to the generous support of fellow YLE community members. To support the effort, subscribe or upgrade below:

Subscribe now

The World Cup kicks off Thursday, pulling millions together in celebration, but where crowds gather, pathogens follow. We’re debuting a new section on the health signals worth watching. Also on the move: a parasitic, flesh-eating fly eradicated in the U.S. in 1966 has found its way back (yes, it’s as terrible as it sounds). And 48 million people are facing serious heat risk. Good news is in the mix, too.

Here’s what’s going on, and most importantly, what it means for you.

Health “weather” report

Ticks are still increasing, and all respiratory diseases are declining to very low levels.

Things are heating up

This week, 48 million people will face “major” heat risk, and 100,000 will face “extreme” heat risk.

When it comes to extreme heat, it’s not just about the temperature you see on your weather app. While 120 degrees in Phoenix isn’t great, 90 degrees in New York can be worse.

This is because the risk to your health is due to heat imbalance. That’s when your body produces more heat than it can release. Normally, sweat helps cool us down. But when it’s hot and humid, sweat doesn’t evaporate as easily. The air is already packed with moisture, making it harder for your body to cool itself and raising the risk of illness quickly.

What this means for you: The following people should take action when their area is “orange” or higher. Everyone else, start taking action in “red.”

• People taking medications that impair heat regulation: Certain drugs interfere with sweating, hydration, or heart function, and can even reduce your thirst sensation. Check out the list here.

• Older adults: Aging reduces the body’s ability to sweat and regulate temperature.

• Infants and children: Smaller bodies heat up faster, and young children may not recognize or communicate early symptoms. Kids with asthma are at high risk.

• People with chronic diseases: Underlying conditions like heart disease strain the body’s ability to cope with heat stress.

• Pregnant women: Pregnancy increases metabolic heat production, making it harder to stay cool. More here.

• Outdoor workers and athletes: Prolonged physical activity in hot environments increases internal heat production.

• People experiencing homelessness: Continuous exposure to heat, dehydration risk, and limited access to cooling or hydration increases vulnerability.

Check the HeatRisk tool to know when to avoid strenuous activity. Stay hydrated. Watch for signs and symptoms of heat stroke. Check your urine color.

Be smart with fans: Fans can help when it’s moderately hot by circulating air and helping sweat evaporate. But once temps climb above 90°F fans may actually blow more hot air onto you, increasing heat stress.

Healthy Cup: Let the games begin!

The World Cup officially kicks off Thursday! YLE is playing a key role at the national Health Security Operations Center, and each week, we’ll share what we’re seeing in the data for those heading to the games or simply curious about what happens when millions of people mix.

While we wait for the games to start, epidemiologists are watching signals at and around base camps and practice games this past week.

The risk remains low, but three signals are garnering attention for now:

• Measles continues to spread in all three host countries, with a significant ongoing outbreak in Mexico. Seven base camps and practice games are near outbreaks, and these teams and their fans will soon disperse to other locations for the tournament. Make sure you’re up to date on the MMR vaccine and protection.

• Norovirus (nausea, vomiting, diarrhea) is declining nationally, with one notable exception: a sharp increase in the South that’s unusual for this time of year and worth watching. This is very contagious, and hand sanitizer won’t work. Wash your hands with soap and water.

• On heat… There was significant public concern about FIFA banning water bottles, which could become a big deal for heat-related illnesses. But on Friday, FIFA clarified (or walked back) its policy, saying attendees are allowed one 20-ounce (591 mL) unopened, soft-plastic disposable bottle (think: a bottle from a vending machine). Drink up.

We will be back next week for more.

Spotlight: Screwworm. The fly has landed.

Five cases of New World screwworm have been confirmed in the U.S. Texas declared an emergency, and Canada immediately restricted livestock imports. This bug could quickly turn into a big deal, and scientists have long warned about its return (I am surprised it didn’t come sooner, to be honest).

I called arbovirologist Dr. Miguel Arturo Saldaña in Texas to help break it down.

Screw… what?

New World screwworm (NWS) is a parasitic fly that was fully eradicated from the U.S. in 1966. It lays eggs in the open wounds of warm-blooded animals. When the eggs hatch, NWS larvae burrow into living flesh. It’s exactly as bad as it sounds, and is fatal if untreated.

How did we keep it out?

Starting in the late 1950s, scientists used the Sterile Insect Technique (SIT): mass-producing sterile males and releasing them to outcompete wild males, collapsing the fly population. It works because female flies mate only once.

Eradication moved down country by country from the U.S through Mexico and Central America over decades, eventually pushing NWS all the way to the Darién Gap in Panama (a remote landbridge of dense, mountainous rainforest). The U.S. and Panama maintained a binational barrier there, dropping roughly 20 million sterilized flies across six flights per week. For decades, it held.

But, for the past few years, it’s been crawling back up, and now, as predicted, to the U.S.

Why is it back?

A combination of factors:

1. Cattle smuggling. NWS detections in Panama spiked from 25 cases per year to more than 6,500 in 2023, driven largely by cattle movement outside sterile fly zones.

2. U.S. federal funding cuts. In early 2025, roughly 15,000 USDA positions were eliminated, and a USAID-funded monitoring project was terminated. Warnings passed as the pest moved north through Mexico.

3. Loss of expertise. In many countries, veteran veterinary entomologists have retired without replacements, taking decades of specialized knowledge with them.

Why does this matter?

• NWS spreads fast. A single female lays 200 to 300 eggs per clutch every three to seven days, up to 15 clutches in her lifetime. Eggs hatch within 24 hours; larvae feed for up to 7 days.

• Human cases are rare and treatable when caught early. The most recent U.S. case was a traveler who returned from El Salvador last year and recovered. Pets can also be affected.

• The bigger concern is the food system. Health and the economy are tightly linked. A 1976 Texas outbreak, a spillover from Mexico, affected 1.8 million livestock. A comparable outbreak today could cost Texas alone $1.8 billion, with losses across NWS’s historic range potentially exceeding $10.6 billion per year, and over $100 billion in broader U.S. livestock economic activity is at stake.

How do we stop it?

Same as before: SIT. Mexico is refurbishing retired rearing facilities to resume sterile fly production by summer 2026. A new U.S. facility in Texas will produce up to 300 million sterile flies per week, though experts estimate 400 to 500 million will be needed for full eradication. Ramping to capacity could take 18 months to two years. Panama is sending SIT males to the U.S. in the meantime.

What this means for you

The biggest concern is livestock, particularly cattle. Here are some tips to keep them healthy. To everyone else, the beef you eat is still safe.

Stray dogs and wildlife are also at risk; pets can be exposed too, but really only in agricultural areas. Ensure pets are on flea & tick prevention from the FDA-approved list, as products containing afoxolaner (dogs) or esafoxolaner (cats) can prevent NWS infection.

For people, risk is not uniform. Agricultural workers in the Southern states, particularly those with open wounds, sores, or skin breaks, are the most vulnerable, as flies are attracted to any open wound.

For everyone else, risk remains very low.

Good news

As always, ending on a lighter note:

• Melinda French Gates pledged $215 million to women’s health. Specifically, expanding contraceptive access, maternal care, and menopause research globally, pushing her total investment in women’s health past $600 million over the past two years.

• An experimental personalized skin cancer vaccine cut the risk of melanoma returning or causing death by 49% after five years when used in combination with immunotherapy. The vaccine is custom-built for each patient using genetic information from their own tumor, teaching the immune system to recognize and attack it. The vaccine still has a while to go through clinical trials, but this is welcome news given the increasing skin cancer rates.

• Inhaled insulin approved for kids with diabetes. The FDA approved inhaled insulin (Afrezza) for children ages 6 and older with diabetes. This is the first needle-free insulin option for pediatric patients in over 100 years. It’s a mealtime insulin delivered via a small portable inhaler, replacing the multiple daily injections kids currently need at meals. Pediatric patients and parents of younger children reported greater treatment satisfaction.

Bottom line

Lots of people and animals are moving, and with them, diseases. We’re keeping an eye on it all and will keep you informed.

Love, YLE

Your Local Epidemiologist (YLE) comprises a team of experts, ranging from physicians to immunologists to epidemiologists to nutritionists, working together with one goal: to “Translate” ever-evolving public health science so that people are well-equipped to make evidence-based decisions. YLE suite of newsletters reaches over 475,000 people across more than 132 countries. This newsletter is free to everyone, thanks to the generous support of fellow YLE community members. To support the effort, subscribe or upgrade below:

Subscribe now

I’ve sat in many classrooms as a student over the years. In none of them was I taught how to communicate in ways that best reach and meet the needs of the audience I was addressing. Particularly if that audience wasn’t scientists.

I learned through failures and experience, and by seeking out guidance where I could find it. But it shouldn’t be this hard.

It’s time to change this for our entire field. It’s time to go beyond the communications team at our institutions. Every scientist and community organization should know how to “translate” science to their community. And sure, some of us will remain in the lab, but some brilliance needs to be unleashed so more science can reach people, and more people can reach science.

The Evidence Collective recently provided data communication training, and not only was it insanely fun, but also, for the first time, I sensed a deep hunger. It gave me hope: scientists are no longer just trying to figure out where we lost trust; now they want to do something.

Here’s a peek at some of the things we covered, and things you should consider when working to better engage your communities.

Read more

So what’s going on with sunscreen? I called Dr. Michelle Wong, an Australian chemist, to help highlight the scientific nuance in sunscreen discussions.

Here’s what we know about sunscreen, what we don’t know, and what it may (or may not) mean for you.

Is sunscreen effective against skin cancer?

Nuance is needed, but yes.

Mechanistically, sunscreen makes sense. UV exposure is the main cause of skin cancers, especially in lighter skin tones, and sunscreens reduce the UV that reaches the skin. In laboratory studies, sunscreen reduces DNA lesions that accumulate over time and eventually lead to cancer.

When we look at “real-world” studies among humans, though, there is mixed evidence of sunscreen’s effectiveness against cancer. Two meta-analyses that pooled all these studies found no effect. However, this is hard to measure as most people apply less sunscreen than is recommended.

If we pull out the most rigorous studies (randomized controlled trials, or RCTs) that followed people over a long period of time, there is a positive effect:

• A long-term Australian RCT (15+ years) found daily sunscreen use reduced squamous cell carcinoma by 40% and roughly halved new cases of melanoma a decade later. No reduction was seen in basal cell carcinomas. However, the limited number of melanomas makes this finding less clear.

• RCTs have also found that sunscreen use reduces pre-cancerous spots (actinic keratoses) and moles in children (a risk factor for melanoma later in life).

Is sunscreen effective against photoaging?

This is a clear yes. Evidence from many studies across diverse populations, including a large RCT, shows that sunscreen prevents signs of photoaging, such as wrinkles and pigmentation.

But DIY sunscreens don’t work well

The chance of you consistently getting sunscreen in your home kitchen is… not great. Scientists estimated the highest SPF achieved in DIY SPF is 6.

DIY sunscreens don’t work for two reasons:

1. Sunscreen developers use special grades of zinc oxide with very small particles, which absorb more UV. These powders are also often coated to improve dispersion, while DIY recipes usually specify “uncoated” powders.

2. Even with the right ingredients and equipment, sunscreen formulators must optimize the formula extensively to achieve consistently high SPF—sunscreens are considered one of the hardest products to create!

What about the risks to the environment, like reefs?

“Reef safe” is a marketing term; there is no official standard behind it.

The term arose from a deeply flawed 2015 study, which led to public pressure that resulted in bans on specific sunscreen ingredients, usually oxybenzone and octinoxate, in some places, such as Hawaii.

But, there’s no good evidence that sunscreen harms coral, except in laboratory experiments where coral is exposed to unrealistically high concentrations. In 2022, the National Academies convened many leading environmental scientists to review evidence on sunscreen’s environmental impacts and compile it into a 400-page report. They confirmed what leading coral scientists stated when the original 2015 study was published: the impacts of sunscreens pale in comparison to far more significant stressors, like warming weather.

Why does the U.S. have fewer sunscreen ingredients than other countries?

Long story short: animal testing.

Sunscreens are one of the most scrutinized products we put on our skin— they’re regulated as drugs in some regions (the U.S., Canada, Australia), and a special category of cosmetics in others (European Union, Japan, Korea).

Historically, getting a new sunscreen approved by the FDA required large-animal studies that include hundreds of animals and over a year of testing to assess actual tumor development.

In other regions like the EU and Australia, a broader range of evidence could be considered for ingredient approval, including smaller, shorter animal studies, in vitro testing, and “real-world” population data.

Since sunscreens are cosmetics in many parts of the world, their ingredients fell under cosmetic animal testing bans. These took effect before the FDA pathway tests could be conducted for the newer sunscreen ingredients, so U.S. approval was never pursued. This has led to a bustling gray market for imported sunscreens containing newer active ingredients—these can provide high protection while allowing for more lightweight, elegant textures. They’re also designed to be inherently safer and less allergenic, with structures that absorb even less through skin. (More on this below.)

The good news: in the U.S., H.R. 5371 passed in late 2025, enabling the FDA to consider broader evidence, such as historical safety data and non-animal testing methods, when evaluating the safety of sunscreen ingredients. In the coming months, bemotrizinol (bis-ethylhexyloxyphenol methoxyphenyl triazine, or BEMT) may be the first new sunscreen ingredient approved since 1999. It’s one of the most popular “chemical” sunscreen actives used outside of the U.S., providing broad protection against both UVB and UVA.

Hopefully, other sunscreen ingredients will follow!

What about ingredient safety?

Differing regulations around the world have also led to confusion around sunscreen safety.

While there are two types of sunscreen, most questions are about “chemical” sunscreens due to FDA whiplash.

Note: Chemical sunscreens (e.g., oxybenzone, avobenzone, octinoxate) are carbon-based and are usually dissolved in the sunscreen formula, while mineral sunscreens (zinc oxide, titanium dioxide) are inorganic and found as solid particles. Both types of sunscreen largely work by sitting on the skin's surface, where they absorb UV radiation and convert it into heat.

For a long time, the FDA’s official stance was that the amounts of “chemical” sunscreens absorbed into the bloodstream were too low to pose serious health risks (defined as a carcinogenic risk greater than 1 in 100,000 after a single dose). They were thus considered safe by default, and detailed safety studies weren’t required. However, new FDA studies in 2019 and 2020 found that blood levels were actually higher than previously thought.

Importantly, this didn’t mean sunscreens are unsafe, but the FDA has requested more data to confirm their safety. Originally, this meant new large-scale animal studies would be needed, which would jeopardize the use of these ingredients in countries with animal testing bans. The recent passage of H.R. 5371 allows alternative studies to be used by the FDA to confirm safety, bringing sunscreen regulation more in line with other regions (the exact details should be issued soon). While in this regulatory limbo, these sunscreen ingredients remain on the U.S. market.

Although this may sound scary, sunscreen safety assessments from other parts of the world are reassuring. The EU and Australia draw on a broader evidence base, and because studies from the 1990s had already flagged blood absorption of chemical sunscreens, that was factored into their safety assessments long ago. And, every ingredient commonly used in U.S. sunscreens has been reassessed in the EU or Australia within the past six years. All were deemed safe.

Why not just use mineral sunscreen?

For those who prefer the feel of mineral sunscreens or are sensitive to particular chemical sunscreens, these can be a great option. And given the seemingly uncertain risks associated with chemical sunscreens, mineral sunscreen may seem like a safer, more appealing alternative.

However, with mineral sunscreens, keep in mind a few things, too:

• Unscrupulous marketing. Australia’s TGA has recently warned that campaigns promoting zinc-based sunscreens “often present incomplete and alarmist narratives about sunscreen ingredients.”

• Feel and appearance: When applied properly, mineral sunscreens appear white on the skin and tend to feel heavier than chemical sunscreens.

• Underapplied: The heaviness and white cast mean they tend to be underapplied. This results in far lower protection and a higher likelihood of sunburn.

• “Hidden” boosters: Due to these drawbacks, there are often hidden “SPF boosters” in mineral sunscreens. These are modified versions of chemical sunscreens, but do not need to be listed as active ingredients and do not undergo the same approval or quality control processes. Although they are likely still very safe, they can be difficult for people with sunscreen allergies to spot.

• Mineral sunscreens are inherently less stable. The particles are much denser than the other ingredients, which means they tend to clump and settle, and small changes in the recipe can throw off the whole product. A recent example: the 2025 Australian sunscreen scandal, in which some zinc oxide sunscreens turned out to provide far less protection than labeled, triggering widespread recalls and a major overhaul of sunscreen regulations.

So what do we do?

The health policy holds strong: sunscreen’s known benefits outweigh the unclear risks, and there are pros and cons to both types of sunscreen actives. Ultimately, the best sunscreen is the one that you will use a lot, regularly.

Overall, keep in mind:

• There are far more similarities than differences between chemical and mineral sunscreens in terms of effectiveness and safety. The main differences are aesthetic.

• “Broad-spectrum” sunscreen is best. The SPF rating on American sunscreen bottles primarily indicates a sunscreen’s ability to block UVB rays, the most damaging type. Some sunscreens in the U.S. don’t cover UVA rays well. Sunscreens labeled “broad spectrum” have a better UVA/UVB protection balance.

• Adequate application is key. The reliability of SPF testing has been in the spotlight recently, with some regions proposing scrapping specific SPF numbers altogether. While SPF 30 will always let in twice as much UV as SPF 50, the differences become much smaller with adequate application: for an adult, aim for one teaspoon for each limb, one for the front of your body, one for your back, and one for your head.

• Vitamin D can still reach the skin. High SPF sunscreens are designed to filter out UVB rays, the exact type of rays needed to produce Vitamin D in our bodies. However, sunscreen doesn’t block all of these rays, and its application is uneven because humans are humans. Unless you are very diligent with daily sunscreen application, including in winter, it’s unlikely that sunscreen will affect your vitamin D status. We also get Vitamin D from food sources.

For sun protection, layers are the name of the game. Sunscreen should be thought of as your last line of defense against the sun.

Bottom line

Sunscreen can help fight skin cancer and prevent photoaging. The nuances can feel paralyzing, but ultimately, the best type of sunscreen is one that you will use a lot of, regularly.

Slip, slop, and slap.

Love, YLE and MW

Dr. Michelle Wong is an Australian chemist and fellow science educator who addresses the top sunscreen rumors circulating widely these days.

Your Local Epidemiologist (YLE) comprises a team of experts, ranging from physicians to immunologists to epidemiologists to nutritionists, working together with one goal: to “Translate” ever-evolving public health science so that people are well-equipped to make evidence-based decisions. YLE suite of newsletters reaches over 475,000 people across more than 132 countries. This newsletter is free to everyone, thanks to the generous support of fellow YLE community members. To support the effort, subscribe or upgrade below:

Subscribe now

This left plenty of room today for good news and a time to celebrate (quite literally, as you will see below) scientific advancements, which have become my favorite section of the newsletter.

Let’s dive in.

Disease weather report

Ticks are… increasing again

After a few unusually eventful weeks, ticks are still keeping us on a rollercoaster. Emergency room visits for tick bites dipped briefly, then rose significantly again. We haven’t hit a record-breaking peak, but the season is running earlier than usual, so the cumulative burden is mounting. If this pace continues, it’s shaping up to be a rough tick season overall.

Those in the Northeast are feeling the brunt of it, followed by the Midwest. Although ticks are really everywhere.

What this means for you: Enjoy the outdoors! But if you’re in a tick-prone area, take that extra minute to do a tick check. The most important thing is removing the tick properly (use fine-tipped tweezers, grab close to the skin, pull upward, no twisting, no Vaseline, no matches). Then watch for symptoms: fever, rash, fatigue, joint aches. If you find an attached tick and are in a high-risk area for Lyme disease, it’s worth calling your doctor if it was attached for more than 36 hours. Here is a YLE deep dive on ticks.

Common colds peaked

We are finally reaching a point where almost all respiratory viruses are on the decline. Common cold viruses appear to have peaked after a higher season than last year.

PIV (parainfluenza virus) is also nearing its peak, which is worth noting for a slightly different reason. Unlike the common cold, PIV is particularly significant for babies, as it is a leading cause of croup and bronchiolitis. As you can see in the graph below, it is less common, though.

What this means for you: If you’re sick, it’s likely the common cold. Rest and fluids really do help boost your immune system.

Measles keeps on ticking along

I haven’t given an update in a while. While the acceleration has slowed down, measles is still spreading. It’s basically endemic at this point: jumping from unvaccinated pocket to unvaccinated pocket.

In the U.S., there are three active outbreaks public health officials are paying attention to:

1. Utah is in its eleventh month with active community transmission.

2. Virginia is where my eyes are right now. The outbreak is still small (64 cases) but growing quickly, with 21 cases in the past week. The vaccination rate in the community (Buckingham County) is low (84.9%).

3. Pennsylvania outbreak with 38 cases (six new cases in the past week).

What this means for you: If you’re up to date on vaccines, you remain very well protected. If you have a child under 12 months old and are in/around these areas, they can get vaccinated early. Here are the top 10 questions on measles protection answered.

Spotlight: Covid-19 virus and vaccines

Every summer since Covid-19 arrived, we have had a wave. And lately, summer waves are larger than winter ones (but continue to decline in severity due to immunity). Here’s where things stand.

What’s the current Covid situation? Levels remain very, very low. There may be a slight increase in some areas if you squint closely at the data (like in Texas and Florida, and maybe the Midwest), but it’s not showing up across all metrics. In other words, we’re not in a wave yet.

The Cicada variant (BA.3.2) received some attention a few weeks ago but has been circulating for some time without making much of an impact. The growing variant is XFG, which is still a descendant of Omicron.

Should I get a spring vaccine? The recommendation stands: vulnerable individuals, particularly those over 65, should still get both a fall and spring vaccine. Year over year, vaccination continues to provide 50–60% additional protection for high-risk individuals compared to those who skip it. If you’ve been trying to time a shot before the next wave, that window may be approaching.

Will we have a Covid-19 vaccine this fall? Yes, I think so, but the path to get there will be bumpy.

Think of our annual respiratory vaccine rollout as a giant domino setup. When the first domino falls—usually in February—the rest follow in a smooth, synchronized sequence, ending with shots in arms by early fall.

Last week, external advisors to FDA met to recommend an updated strain for this fall’s vaccine and voted to use the XFG strain. This differs from the WHO’s recommendation (LP.8.1). Strain differences between the U.S. and WHO aren’t entirely unusual—the U.S. typically targets the closest-matching strain for precision, while the WHO prioritizes broader coverage to accommodate countries with less flexibility to update quickly. Immunologically, the U.S. approach makes more sense.

But now the subsequent dominoes in the process of getting a vaccine may start wobbling.

The next step would normally be an ACIP meeting, but there is currently no ACIP, which is unprecedented. Two possible pathways are now in play, and both may end up being used:

1. The standard federal pathway (blue below). Either an ACIP is chartered (a long shot), or the ACIP step is bypassed entirely, and the CDC director signs off on the vaccine independently.

2. An alternative pathway (purple below) was developed last year by external organizations in response to federal disarray. Many states have already decoupled from ACIP and are instead following guidance from professional bodies like the American Academy of Pediatrics and the Vaccine Integrity Project (VIP). VIP will be meeting soon to review the evidence, enabling professional organizations to issue their own recommendations, which will then prompt health systems and physicians to begin ordering vaccines.

   
   Key limitation: This pathway doesn’t resolve the issue of ordering and distributing vaccines purchased through federal programs, most notably Vaccines for Children.

What this means for you: If you’ve been trying to time your Covid-19 spring vaccine before a wave, that moment may be getting close, though it’s still unclear. As for fall, I’m confident vaccines will be available, but expect some confusion and uncertainty in the run-up. But they will be there.

Good news, and lots of it

1. Standing ovation for pancreatic cancer survival study. During a national cancer convention (ASCO) over the weekend, results from a Phase III clinical trial of a pancreatic cancer drug were announced, and the room erupted in applause. This is really rare, but it also signals the beauty of the discovery. What did scientists find? Patients taking a new, experimental drug lived nearly twice as long as patients offered standard chemotherapy. Daraxonrasib reduced the risk of death by 60% compared with chemotherapy. Pancreatic cancer is a devastating disease, with a low survival rate, and is really hard to target with drugs. While this isn’t on the market yet, there seems to be major hope on the horizon.

2. Major health insurers announced they will cover all vaccines at no cost through 2027, regardless of what ACIP, federal disarray, and ideological preferences say. This is incredibly abnormal, as they usually wait for federal guidance, but great news and, quite frankly, just the right thing to do.

3. Americans are increasingly treating mental health like physical health. This news is a little older, but worth celebrating as we close out mental health awareness month: More than one in three Americans said they planned to make a mental health-related resolution this year, with younger adults ages 18–34 leading the trend at 58%. Growing cultural normalization of mental health care is itself a public health win, as stigma has historically been a major barrier to treatment.

4. An obesity drug may not just “melt fat,” but also decrease inflammation that drives heart disease, joint pain, and diabetes. Lilly is testing a new drug called retatrutide, a weekly injection that targets three hormones for weight loss. In its latest clinical trial results, released this month, participants lost an average of 71 pounds over about a year and a half and also made significant improvements in markers of heart disease and overall inflammation. The addition of glucagon targeting helps the body to burn fuel, enabling greater weight loss and likely accounting for the additional benefits over earlier GLP-1 drugs. The drug isn’t approved yet, and more safety and effectiveness data are coming, but the early results are strong. If future trials hold up, this could become a single-shot treatment for obesity, diabetes, inflammation, and their related health problems all at once.

5. Global teamwork (without the U.S.) towards health. The 79th World Health Assembly—whose theme was “Reshaping global health: a shared responsibility”—ended with 193 member states (notably the U.S. is no longer a member) agreeing on 20 decisions and passing 13 resolutions on a variety of health issues, including stroke, liver disease, tuberculosis, antimicrobial resistance, diagnostic imaging, emergency care, precision medicine, and radiation.

6. Ebola patients were discharged from the hospital. Five patients were cured of the Bundibugyo Ebola virus: four left the treatment center today, and another had already returned home. As Helen Branswell, from STAT, noted, “communities can distrust treatment centers, because loved ones go in & often don't come out alive. Hopefully, word of survivals will encourage people to seek care rather than staying home. Improves their survival chances & lowers risk to family members.” Ebola can be defeated.

Bottom line

While ticks and common colds are brewing, the quieter week allows us to recognize the quiet science marching forward. This week brought results targeting the two leading killers of Americans, heart disease and cancer. That is always worth celebrating.

Love, YLE

Your Local Epidemiologist (YLE) comprises a team of experts, ranging from physicians to immunologists to epidemiologists to nutritionists, working together with one goal: to “Translate” ever-evolving public health science so that people are well-equipped to make evidence-based decisions. YLE suite of newsletters reaches over 475,000 people across more than 132 countries. This newsletter is free to everyone, thanks to the generous support of fellow YLE community members. To support the effort, subscribe or upgrade below:

Subscribe now

I try to keep Fridays reserved for paid YLE subscribers, and particularly the professionals and trusted messengers who are guiding households, communities, and patients. My goal is to help make your life a little easier.

Here are the top four questions we received this week to help you feel confident navigating what’s going on:

1. I’m traveling to [X] country in Africa. Should I cancel my plans? Dr. Emily Smith is supposed to go to Tanzania, so I called her, and together, we created a decision tree.

2. Do airport checks really work? And if not, what is being done?

3. What is the status of the Covid-19 vaccine?

4. What’s going on with the U.S. Preventive Services Task Force?

Read more

Here’s an attempt to keep you up to speed and, more importantly, what it means for you and your community.

But first, an announcement: World Cup

The World Cup starts in 15 days (not like anyone is counting down), and we are hanging TVs in the Health Security Operations Center. It’s going to be a gorgeous, chaotic celebration of basically every culture on earth. And it’s going to take a team effort—from communities to individuals, from public health to health care—to keep people healthy.

That’s where you come in.

If you’re going to the games or live within 30 miles of a stadium, we would love to hear from you. Sign up for a weekly survey here. Thanks to the more than 1,280 people who have already signed up…you will be hearing from us soon!!

Global disease “weather report”

Hantavirus: Two more cases

The global count of cruise ship passengers with hantavirus has now increased to 13 cases (11 confirmed), with three deaths. The two new cases are overseas and among people who were already quarantining:

1. A crew member in the Netherlands.

2. A Spanish national passenger who was quarantining at home tested positive through daily monitoring. They are now in a biocontainment unit.

In the U.S., everyone remains negative.

There may be more cases, given that the incubation period of hantavirus (the time from exposure to infection) is 45 days. But this week, we will reach a major milestone: the median incubation window is 18 days, and that will pass on May 29.

What this means for you: Your risk from this cruise ship outbreak remains essentially nil at this point.

Ebola rages on in Central Africa

Big thanks to Dr. Craig Spencer, a humanitarian physician who has treated and survived Ebola, for jumping in to provide the YLE community with an update. Craig, take it from here…

The combined confirmed and suspected Ebola cases in DRC are now more than 1,000. All signs are pointing to a very long and catastrophic outbreak in Central Africa:

1. This is a vast undercount. We know this because the test positivity rate is hovering around 50%, only 20% of contacts are being traced (and in some areas, no contacts at all), and more cases keep popping up with no known connection. This all points to widespread and undetected community transmission.

2. This is in only a week of detection. Compared to previous outbreaks, the growth is very fast, as the huge West Africa outbreak in 2016 was first detected at 49 cases and rose to 208 cases a month later. It took four months for that outbreak to reach the size of the current one in the DR Congo.

3. The cases are spread out across 16 health zones. There are now multiple epicenters, making containment very difficult.

Next door in Uganda, the case count is seven. While this number is low compared to DRC, a concerning development is that two health care workers recently tested positive with uncertain exposure histories. If they weren’t treating known Ebola cases, this means it’s spreading undetected in Uganda as well.

On the ground, backlash, including the burning of health centers, has emerged, a pattern seen in nearly every outbreak and rooted in deep community distrust. It often stems from outside actors working in communities without fully understanding or addressing local priorities. Affected populations may recognize the severity of Ebola while still holding other concerns as more pressing, such as where their loved ones are buried. Community trust is essential to an effective response, but difficult to build during an active emergency. It is best established long before a crisis begins.

U.S. priorities are made clear, and may backfire. The U.S. Administration has shown that its first priority is keeping Ebola out, with helping end the outbreak in the DRC a secondary concern. That's meant travel restrictions broader than anything we've imposed before — covering travelers from across the region, and reportedly some green card holders and permanent residents as well.

For example, just these past two days, news broke that high-risk American travelers will be subject to a mandatory quarantine in Kenya before they are allowed to return. If an American is infected, the U.S. government plans to send them to a hospital it is standing up from scratch in Kenya. (Currently, Americans who were in the area are allowed to return but are diverted to three airports—Houston, Atlanta, and DC—for further screening.) Past administrations have used travel notices and stepped-up screening; this goes much further.

At first blush, these strict precautions may sound prudent. But this approach could backfire in three ways:

1. Restrictions this blunt give people every reason to hide where they’ve been and whom they’ve been near — making the people we most need to find harder to track, not easier.

2. They also breed a false sense that this is someone else’s problem. But diseases are humbling. They find the small cracks in even the most impenetrable-seeming defenses.

3. Lives lost. There is no treatment for this Ebola strain, which means survival depends heavily on the quality of the health system. We have that system in the States, but we are choosing not to use it for infected Americans.

This is unbelievable and infuriating. (See a deeper dive from me here.)

The only real way to lower the risk to Americans — and everyone else — is to end the outbreak in the DRC and across the region.

What this means for you: If you have travel plans to this region, it’s time to cancel them. This is a high-risk situation in Central Africa, and CDC released a Level 4 Travel Advisory. There is also great uncertainty if and when the Administration will let you back in.

To the general public in the U.S., your risk remains very, very low right now.

U.S. disease “weather report”

Ticks: past peak season?

Good news, especially for people in the Northeast and Midwest: tick numbers continue to decline. Though we are at the peak of the season, this unusually early year is trending favorably.

Heat-related illnesses in the North

Heat risk is certainly not blanketing the entire country yet, but this week it will be moderate in the Midwest and the Southeast.

What this means for you: Be sure to check the CDC HeatRisk tool. A red day isn’t the best day for that soccer game for a kid with asthma, and a stretch of orange days is a great time to check on your elderly neighbor.

Common colds surging

As far as respiratory viruses go, the only thing really going around right now is the common cold. It is higher this year than last year, but should peak very soon before returning this fall.

Spotlight: Chemical plants

Over the weekend, YLE California covered the serious situation that unfolded around a chemical plant in Orange County, California. Thankfully, the worst-case scenario (a chemical explosion) was mitigated, but only through luck. The health implications in a densely populated area could have been catastrophic.

As the situation was winding down, another chemical explosion struck Washington State. This one was fatal. Health officials say the risk to surrounding residents from chemicals in the air and ground remains low, though the community deserves far greater clarity.

Clean air and clean water consistently rank as Americans’ top public health concerns — yet when chemical disasters strike, communities are too often met with reassurances rather than transparency and accountability. Residents near the 2023 East Palestine, Ohio train derailment, for example, are still waiting to understand the long-term impact on their health, with few clear answers.

What this means for you: Many are wondering if facilities processing potentially dangerous materials are in their neighborhoods. This interactive map allows you to enter your ZIP code and see all facilities monitored by the EPA, including any violations.

Good news

• Ebola vaccines and treatment for the Bundibugyo species are in development. Two vaccine platforms are being explored, at least one of which may be deployable in as little as 2 months. One vaccine is being developed by Oxford, and the other uses the same biotechnology as the FDA-approved Zaire species of Ebola. (It may provide cross-protection, but it’s unclear at this point.) On the treatment side, two promising monoclonal antibody cocktails are likely to be deployed, though doses are limited and logistical hurdles remain significant challenges. Anni over at The Biotech Tea had a great explainer about the Ebola vaccine gap, if you want to read more.

The Biotech Tea

The Ebola vaccine gap, reading vessel damage, & the Makary exit

🗝️ Paid subscribers get the Biotech Term of the Week at $30/year (~$2.50/month). I try to keep it intentionally accessible, but if cost is ever a barrier, send me a message. A few people asked about expensing your subscription, so I put together a short email template…

Read more

2 months ago · 10 likes · Annicka Evans, PhD

• Polycystic ovary syndrome (PCOS) has been officially renamed polyendocrine metabolic ovarian syndrome (PMOS), following more than a decade of debate and input from roughly 22,000 clinicians, researchers, and patients worldwide. This is good because the old name was medically misleading, leading to patients without visible cysts being dismissed or overlooked entirely. The WHO estimates that 70% of people with the condition remain undiagnosed. A more accurate name should improve recognition, reduce stigma, and ultimately help the millions of people living with this condition get diagnosed and treated sooner.

Poll

Bottom line

Public health situations are everywhere right now. Staying healthy takes public health professionals and systems working tirelessly behind the scenes and each of us showing up for our neighbors and communities.

Love, YLE

Big thanks to Ed Nirenberg for staying on top of the Ebola vaccines, Hannah Totte for all the figures, Dr. Craig Spencer for the Ebola insight, and Dr. Matt Willis for covering the chemical situation in CA.

Your Local Epidemiologist (YLE) comprises a team of experts, ranging from physicians to immunologists to epidemiologists to nutritionists, working together with one goal: to “Translate” ever-evolving public health science so that people are well-equipped to make evidence-based decisions. YLE suite of newsletters reaches over 475,000 people across more than 132 countries. This newsletter is free to everyone, thanks to the generous support of fellow YLE community members. To support the effort, subscribe or upgrade below:

Subscribe now

This made our most recent webinar incredibly special. We heard directly from four rockstars—our own Liz Marnik, Executive Director of The Evidence Collective, a program under YLE; Anna Culbertson; Kelsey Fox Bennett Boyd; and Kristin Oliver—who were raised unvaccinated and eventually changed their minds. (Liz shared more of her experience here in the NYT.)

Their stories show us how we can improve conversations with people who might be vaccine hesitant and, most importantly, foster empathy and understanding for the process of changing one’s mind.

Paid subscribers can access the full webinar recording above—I know many of you have been waiting for it!

Five key takeaways

1. Changing minds takes time. Nobody in this conversation went from having never been vaccinated to running to get vaccines overnight. Over time, small moments add up: a coach’s offhand comment, a college requirement, becoming a parent, a story from a friend. Plant seeds and trust they’ll grow.

2. Vaccine decisions play into identity. Whether to get vaccinated is tied to whom they trust and where they belong. People’s reasons for not getting vaccinated vary—like every other aspect of identity, there’s more heterogeneity here than we might expect. Acknowledging the identity piece, instead of treating this as a debate over facts, is a step toward meeting people where they are.

3. Close the language gap. Panelists consistently felt safest with people who could meet them on their terms. Being open to terms like wellness, “root cause,” and prevention makes a difference—in truth, these are things we all care about, and familiar language supports trust-building. So does being curious about how alternative medicine and holistic approaches may complement Western medicine.

4. Get genuinely curious about sources. We are exposed to information constantly, and our online environments make it easy to sound authoritative without vetted experience. Some people have had dismissive or harmful experiences with the medical system that understandably influence their perspectives today. Questions like “Where did you hear that? What made you trust that person? Can we listen to that podcast together?” show true curiosity. Asked without judgment, these questions signal that you’re interested in truly understanding, not in winning a debate.

5. You don’t have to be a doctor to be a trusted messenger. Every story in this conversation pointed to the same thing: the people who created cracks in the system that questioned vaccines were not physicians. They were coaches, friends, fellow parents, and people sharing their own stories of going from unvaccinated to vaccinated.

FAQs

Webinar participants asked fantastic questions, but we ran out of time to address them all live! Liz chose four to address here:

Read more

Ebola is often called the disease of compassion by experts like Dr. Craig Spencer. It spreads through direct contact with bodily fluids, which means it spreads when a family member tends to the sick, when a nurse stays at the bedside, or when a community gathers to bury their dead. In other words, it’s spread through acts of care.

But the phrase has been sitting differently lately because this outbreak is spreading not only through compassion but also through the global withdrawal of it. It’s impossible to ignore the quiet (or not-so-quiet) shift from “we” to “me” over the past several years (decades?), now contributing, to some extent, to a body count.

A dangerous myth: Self-interest and global good are opposites

Over the past several years (decades?), a tug-of-war battle has been taking place between individualism and collective responsibility, becoming one of the defining tensions in American identity.

It’s not too hard to understand why. When systems fail people, like through crushing health care costs, stagnant wages, lack of accountability, and governments captured by private interests, people stop trusting those systems. If no one is coming to save you, you learn to save yourself. Sprinkle in profit and power grabs amid the vulnerability of division and isolation, and… here we are.

This personal survival instinct became a governing philosophy, then policy. Fields like public health, which have been built on the basic assumption that society as a whole values a collective approach, have been intentionally targeted. This thinking became so dominant, in fact, that people cheered when a chainsaw was taken to USAID—an organization that built clinics, trained health workers, funded labs, and supported rapid response teams in the places where outbreaks begin. Ebola is one of the first outbreaks unfolding in the aftermath of cutting this global health funding.

The prevailing idea is that what happens on the other side of the world has nothing to do with us. But this idea is a myth, especially when it comes to diseases, for three main reasons:

1. Americans are impacted by this Ebola outbreak directly, as they are being flown to another country to seek care.

2. We live in an interconnected world bound together by supply chains, air travel corridors, and accelerating disease spillovers from animals to humans. No wall can stop a pathogen, and neither can a travel ban.

3. The stakes are also economic. For example, when the U.S. invests in global health research and development, it can yield a sixfold return, including new jobs and economic activity. The Covid-19 pandemic cost 500 times what it would have to invest in proposed preventive measures to reduce disease spillover. The price of prevention is remarkably low, at less than 1% of the federal budget.

This week, the State Department seemed to realize the mistake and announced it will fund up to 50 Ebola treatment clinics in the DRC and Uganda, touting it as an “ironclad” commitment. Sure, treatment centers matter a lot if this actually happens. (As you can see below, the countries don’t even know this is happening.) But what works even better, and is more cost-effective? Helping prevent this in the first place.

True self-interest, rightly understood, is investment in global health. It is a myth that they are at odds.

The ethic of “just because”

But reducing all of this to strategy, or ROI, or soft power is, itself, a shortcoming. Strategy isn’t necessarily why people like the doctors and nurses of Médecins Sans Frontières have spent decades running toward the fire. They put their lives on the line because they simply care.

There used to be a shared value of foreign aid and international cooperation, broadly based on the idea that help was needed. The ROI was compassionate care for others as neighbors, grounded in empathy and equity. The ROI was saving lives and serving. That is enough.

The World Health Organization was built on this. The entire postwar international order, as flawed and incomplete as it often was, rested on the idea that nations had obligations to one another that went beyond what they could extract. That a human life had value that did not depend on its proximity to power, or its usefulness to anyone’s GDP. The value of a life, of all lives, matters and should not depend on where you live.

The Marshall Plan, for example, was not philanthropy because it was strategic. It was simultaneously multiplicative, collective, and synergistic. The people who built it did not find that troubling.

We have lost the animating belief that strangers’ suffering is our concern. That the provision of care is not decided by power but by compassion and collective empathy.

The cost is always paid by the same people

The most heartbreaking thing about all of this is that radical individualism doesn’t distribute its consequences equally. It always funnels suffering downward to the poor, the rural, and the people whose names don’t appear in the articles until they are counted among the dead.

Ebola’s geography is not an accident. Sure, it’s where the fruit bats live, but the cost is high for a reason. The cost lives where the hospitals don’t, where the roads end in mud, and the power cuts out, where the cold chain for vaccines has never been reliable, where the nearest trained physician might be two days’ travel away. It thrives in the gaps left by decades of systematic disinvestment, war, poverty, and a warming climate, and structural adjustment programs that stripped health budgets to the bone. Sometimes international attention arrives, but like many things in public health, it comes in cycles of panic and neglect. Once the cameras leave, so does the money.

The pushback seems to center around power and money. The same countries that hold most of the world’s wealth continue to be the most advanced in terms of health care workers, the number of medical facilities, and their ability to care for infectious diseases like Ebola. There remains a misconception that trickle-down economics and capitalism are the only ways for countries and people to thrive. In an ironic twist, investing and caring for the poorest of the poor first actually benefits all of us more. No matter how you slice the data, collectivism beats out individualism every time.

Research from one of us (Emily Smith) shows that when we start with the poor first, in a trickle-up economy, we actually fare better globally. Within and between countries, starting with the most vulnerable, is advantageous to all of us, fiscally, more than trickle-down capitalistic, individualistic approaches. This is health and wealth. But it only happens when we center the poor first. When the poorest of us are taken care of, we all thrive.

Bottom line

Ebola is called the disease of compassion because it spreads through caring for one another. What we are watching now is what happens when that caring is systematically dismantled. I hope the pendulum finds its way back to a place where compassion and the communal good can, once again, simply exist.

Love, YLE and FNE (ES)

Dr. Emily Smith (ES) is a global health epidemiologist, professor, and scientific communicator. She is the author of the Substack Friendly Neighborhood Epidemiologist (FNE) and the book Science of the Good Samaritan.

Your Local Epidemiologist (YLE) is founded by Dr. Katelyn Jetelina, MPH PhD—an epidemiologist, wife, and mom of two little girls. YLE comprises a team of experts, ranging from physicians to immunologists to epidemiologists to nutritionists, working together with one goal: to “Translate” ever-evolving public health science so that people are well-equipped to make evidence-based decisions. YLE reaches over 425,000 people across more than 132 countries. This newsletter is free to everyone, thanks to the generous support of fellow YLE community members. To support the effort, subscribe or upgrade below:

Subscribe now

There was also a massive fly problem. It was so severe that the Greeks made ritual sacrifices to a deity they called Zeus Apomyios (which meant Zeus Averter of Flies). Before the Games, they appealed to a god specifically designated to keep the insects away.

The conditions were so notorious that ancient philosophers used them as a shorthand for human endurance. Epictetus asked his students: Are you not scorched? Are you not pressed by a crowd? Are you not without comfortable means of bathing? … Have you not abundance of noise, clamour, and other disagreeable things? But I suppose that setting all these things off against the magnificence of the spectacle, you bear and endure.

The World Cup kicks off in less than a month. It will be a magnificent spectacle and, thankfully, we don’t have to sacrifice to Zeus, as public health has advanced enormously in the past century. But the underlying challenge hasn’t gone away.

Here’s what’s happening in preparation and how you can get involved.

The world’s largest event

More than 100 matches will be played across 16 cities in the U.S., Canada, and Mexico over 38 days. Travelers from more than 48 countries will be flying in to watch and celebrate, with an expected 1.5 million additional inbound trips to the country. People will fill stadiums, spill into surrounding neighborhoods, pack bars and parks, and use public transit.

While this is a beautiful moment of celebration and the mixture of cultures, it brings enormous complexities to protecting the public’s health in two primary ways:

1. The sheer number of humans. High density = amplification of disease spread. Also, an influx provides added stress to health systems, like more broken bones, more heat-related illnesses, more (possibly violent) injuries, etc. For example, below are medical encounters before and during the 2022 World Cup in Qatar; they surged.

2. When people mix, diseases mix. New diseases could be introduced that we are not normally exposed to or immune to. A traveler from one region may carry a pathogen that’s routine back home but entirely novel to someone sitting next to them in the stands.

What are the diseases top of mind?

Some disease modelers are hard at work examining more than 80 diseases, and only a few show excess risk. At the top of the watchlist this summer:

1. Measles. This is surging in many parts of the world, and all it takes is one person to find a tightly knit, unvaccinated pocket to start measles spreading like wildfire.

2. Dengue. The U.S. has mosquito populations capable of carrying the virus. We haven’t seen widespread domestic spread, but the combination of summer heat, outdoor crowds, and high travel volume creates conditions worth watching carefully, particularly in southern states like Florida, California, and Texas.

3. High-consequence diseases. Many systems are gearing up to detect Ebola, hantavirus, and other rare pathogens. But the public risk remains low, including for Ebola, simply because of how the virus spreads (through direct contact with bodily fluids). It's worth remembering that the 2014 World Cup in Brazil coincided with the largest Ebola outbreak in history, and there was no outbreak there.

Beyond infectious diseases, heat-related illness may be the least dramatic item on the list, but it’s probably the most reliable risk. Crowds plus sun plus summer temperatures plus physical exertion plus alcohol is a combination that sends people to emergency rooms every year.

So what’s the plan?

Local and state health departments have been preparing. Many have activated their Emergency Operations Centers, which are the same command structures they use for natural events like hurricanes. Data systems are being tuned and tested to catch unusual signals early, before a cluster becomes an outbreak. Hospital systems are coordinating on surge capacity. Rapid response teams are on standby. Weekly coordination calls have already started in many jurisdictions.

This local preparation is essential as they know their communities best. But given movement across state and international borders, a national bird’s-eye view is also necessary to stitch together a broad picture of health around the World Cup.

One national effort in which YLE is playing a central role is the Health Security Operations Center. This will be held in person in Washington, DC, led by Dr. Rebecca Katz at Georgetown University. In normal times, this would reside within the federal government. This is the first-ever non-governmental operations center that brings together academic researchers, technology companies (like Verily and Samsung), and public health departments under one roof.

This will act as an intelligence fusion center pulling in data from wastewater monitoring, hospitals, contextual sources, and social listening. All of these data systems are built as underlying infrastructure, so they can turn on a dime for many diseases. (For example, wastewater monitoring for hantavirus is already turned on.) The goal is rapid detection of emerging health threats, with warnings shared across jurisdictions as early as possible, so people can take the necessary action.

YLE is charged with ensuring that the right information is delivered to the right people at the right time, so they can make the right decisions. This means leading information collection, social and media monitoring, “translation,” and dissemination.

What this means for you

During the games, be aware of your surroundings, consider using DEET, drink plenty of water, and wear a seatbelt. A mask can help in very crowded indoor settings. I will be sure to bring you along for the ride with what we are seeing in the data and what it may mean for you.

If you’re attending a game or live within 30 miles of a host city, we want to hear from you!

• What you’d be doing: Taking a short weekly survey. It’s a few questions about what health topics are on your mind, what rumors or concerns you’re hearing, and what questions aren’t getting answered.

• Why it matters: We will use your responses to directly address the questions and concerns most relevant to you in the Your Local Epidemiologist newsletter. We’ll also summarize the responses for our partners so that local health systems and governments can better address fan and community needs in real time.

• Sign up here, and we’ll follow up with everything you need to get started.

Bottom line

This summer, we will continue a tradition that has lasted for decades. Public health partners, and we will be watching the data carefully in the background so that millions of fans can be scorched, crowded, and thoroughly, joyfully present.

Love, YLE

Your Local Epidemiologist (YLE) is founded by Dr. Katelyn Jetelina, MPH PhD—an epidemiologist, wife, and mom of two little girls. YLE comprises a team of experts, ranging from physicians to immunologists to epidemiologists to nutritionists, working together with one goal: to “Translate” ever-evolving public health science so that people are well-equipped to make evidence-based decisions. YLE reaches over 425,000 people across more than 132 countries. This newsletter is free to everyone, thanks to the generous support of fellow YLE community members. To support the effort, subscribe or upgrade below:

Subscribe now