Explosive foodborne outbreak
It's a real shit show out there: What we know, don't know, and what it means for you.
Well, nothing like the U.S.'s biggest explosive diarrhea outbreak ever to take me out of vacation mode. But I’m getting really frustrated with the coverage, which leaves people struggling to navigate which foods are safe and which aren’t.
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:
I am 72 and been shitting my brains out for 13 days now. I don't travel. I don't eat at fast food restaurants. I don't buy packaged produce. Nearly all my produce is from farmers markets. Awaiting test results. I did have to beg my provider. At least I don't feel sick!
Thank you. Valid and reliable information is vital, in this and in many of the other issues you report on.