Cyclosporiasis from Let's Know Things | Podcast Episode on Podbay

The Centers for Disease Control and Prevention is the main agency tasked with keeping those numbers as low as possible, and the CDC’s Foodborne Diseases Active Surveillance Network, or FoodNet, is one way that they’ve tackled this pernicious, persistent problem since 1995, in partnership with the Food and Drug Administration, the US Department of Agriculture, and 10 state health departments: those of California, Colorado, Connecticut, Georgia, Maryland, Minnesota, New Mexico, New York, Oregon, and Tennessee.

Collectively, this FoodNet network covers about 16% of the US population, which seems like a small number, and in some ways it is, but that grid of laboratories and surveillance sites has typically been capable of detecting foodborne problems before they’ve scaled-up into something more significant, growing from a localized issue into a nationwide outbreak. They’re generally not capable of preventing them outright, but they can keep them relatively small and regionalized.

FoodNet was created in response to a series of huge, deadly E. coli outbreaks in 1992 and 1993, and in contrast to other common methods of detection, which are usually passive and thus a little slow to respond to potential outbreak indicators, this program was built around active surveillance methods, which means proactively gathering data from medical treatment records, hospitalizations, and even individual patient outcomes (including their travel history)—anything they can pair with diagnostic samples to better understand the context surrounding the products that contain dangerous pathogens—and this was intended to help them move faster to identify issues, triangulate the source of those issues, and then implement measures to solve these issues before they harm a bunch of people, as happened during another round of E. coli outbreaks in 2012 and 2013, which sickened dozens of people across multiple states, about half of the afflicted requiring hospitalization, in addition to at least one known death.

At its height, FoodNet tracked 9 pathogens, so it cast a pretty broad net, encompassing the most common and dangerous of these potential vectors, including listeria, campylobacter, shigella, vibrio, yersinia, cyclospora, cryptosporidium, e coli, and salmonella.

In July of 2025, as part of a larger wave of sweeping cuts across the nation’s safety nets, tracking systems, and scientific agencies, the CDC, under the second Trump administration, downgraded FoodNet so that it was only mandatory to track salmonella and E coli—the rest were no longer on the docket, because these agencies no longer had the budget to keep tracking them.

What I’d like to talk about today is a recent, and as of the day I’m recording this ongoing, outbreak of cyclospora-induced cyclosporiasis, what we know about this outbreak, and what might happen next.

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Cyclospora cayetanensis is a protozoan that can infect human beings, and which is usually transmitted via contaminated fruits and vegetables. This contamination is typically the consequence of inadequate sanitation standards, as it’s not transmitted via coughing or blood or anything like that, it’s carried via human feces.

So this parasite gets into a human, sporulates, which means it releases a bunch of spores within its host, and then usually between 1 and 2 weeks after entering its new host, the host develops cyclosporiasis, the disease caused by cyclospora producing all those spores. This disease is notorious for sometimes causing what’s colorfully called explosive diarrhea, alongside general watery bowel movements, intense cramping and severe gas and bloating, and that’s sometimes paired with nausea, vomiting, fever, and dehydration, due to all the frequent, intense, watery bowel-movement-related output.

This is how cyclospora reproduces and spreads: it infects a host, that host has urgent diarrhea for a while, usually more than two days, sometimes as long as several weeks or even a month or more, with all the pain and discomfort and life-disrupting issues you might assume from that sort of persistent symptom, and then it sometimes finds new hosts via that watery output.

Sometimes, cyclospora works its way into food systems because sanitation standards at a particular farm will be not good. Specifically, workers will sometimes not be allowed to take restroom breaks, and they’ll simply do their business right there in the field; so if they’re sick and can’t afford to take a sick day, and might be fired if they do, or if they’re asymptomatic, which some people infected with cyclospora are, they might do their business in the field, unaware that waste can then go on to spread this pathogen into the food system. It’s also possible that someone just doesn’t wash their hands properly after using the rest room, and then gets back to work, picking vegetables or operating at some other level along the food processing and packaging assembly line, and it gets into the system that way.

In a typical year, the United States records around 2,700 confirmed cases of cyclosporiasis, though on occasion it’s as low as just a few hundred cases, the majority of which show up in health records in the Spring and Summer, between May and August. That range includes relatively mild outbreaks, so while this is a persistent issue, it’s also not generally a massive one, at least compared to other pathogens of note. It’s not pleasant for those who come down with it, of course, but not something that has triggered an organized response from the top, because of its meager scale, and because (again, while super unpleasant) people with healthy immune systems generally recover without treatment, even if that recovery can take a while. The biggest risk for most people who catch this disease is dehydration, though immunocompromised people are also sometimes given antibiotics by their doctors, the typical dosage curing about 96% of the people who receive it.

There was a larger-than-usual outbreak of cyclosporiasis in the US in 2020, which caused a confirmed 1,241 cases across the country, a whole lot to land all at once, and there were no reported deaths resulting from that outbreak. Between 2018 and 2021, there were about 6,000 total confirmed cases across the US, so an average of about 2000 per year.

As of mid-July 2026, the CDC has officially confirmed 1,645 cases of this illness, with another 5,100 probable or potential cases currently under investigation. If the majority of those still-under-investigation cases are confirmed, that would mean more people have already been infected as a result of this one outbreak in the first half of 2026 than were infected between 2018 and 2021, which again, is a range that includes the large outbreak that happened in 2020.

Also worth noting about those numbers: that’s federal-level, CDC reporting, and it’s generally understood that there’s a significant lag between local-level data and those that have percolated up to the national level. As of the day I’m recording this, Michigan’s health agencies alone have more than 5,000 confirmed and suspected cases, Ohio has nearly 1,200, and other states, which are still investigating, are seeing dozens of confirmed cases, including 43 in Wisconsin, 69 in Maryland, and a few already, in the early stages of investigation, in Nevada.

Over the past week, officials flagged shredded lettuce sourced from Mexico and sold by a company called Taylor Farms as the likely source of at least some of these cases, and that’s led to a recall on lettuce produced by the company in 27 states. Over the weekend, the CDC found cyclospora in iceberg lettuce from the company’s Mexican operations, as well, and this lettuce was part of a batch that wasn’t included in the recall…

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