{"id":940818,"date":"2026-07-17T09:48:16","date_gmt":"2026-07-17T09:48:16","guid":{"rendered":"https:\/\/www.europesays.com\/us\/940818\/"},"modified":"2026-07-17T09:48:16","modified_gmt":"2026-07-17T09:48:16","slug":"cyclospora-is-causing-explosive-diarrhea-in-the-u-s-one-vegetable-may-be-to-blame","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/us\/940818\/","title":{"rendered":"Cyclospora is causing explosive diarrhea in the U.S. One vegetable may be to blame."},"content":{"rendered":"

Sign up for the Slatest<\/a> to get the most insightful analysis, criticism, and advice out there, delivered to your inbox daily.<\/p>\n

It would be dramatic to say that lettuce is the riskiest vegetable in the produce aisle to eat, but its reputation these days is anything but squeaky-clean. In 2010, about 23,000 pounds of lettuce were recalled due to a multistate E. coli outbreak<\/a> involving Freshway Foods; in 2019, three E. coli outbreaks were traced to lettuces and leafy greens from a specific area of California<\/a>; and in 2020, bagged salads from Fresh Express were linked to an outbreak of Cyclospora. This summer, Cyclospora\u2014a parasite that is giving those it infects explosive diarrhea<\/a> that can last for weeks\u2014is again rearing its ugly head, as many state departments of health report thousands of cases (numbers that, as a rule, undercount the true spread) and the Centers for Disease Control and Prevention suggests that the problem likely won\u2019t be resolved until at least August. Perhaps most alarmingly, we don\u2019t yet know the origins of this current outbreak. But that hasn\u2019t stopped people from assuming, given its tainted history, that the perpetrator is lettuce.<\/p>\n

There has been speculation that nationwide restaurant chains, like Taco Bell<\/a>, and their suppliers may be to blame; meanwhile, health departments are warning people to stay away from (or thoroughly cook) a wide range of produce usually eaten raw, including herbs and berries, in addition to leafy greens. Meanwhile, the International Fresh Produce Association is urging caution<\/a> with reports from state health departments that might be making unfounded assertions about the source of the outbreak. It doesn\u2019t help, either, that this administration\u2019s early decision to gut the CDC, and thus stymie programs that trace these pathogens, have severely hindered our usual means of handling foodborne illnesses.<\/p>\n

Even if lettuce doesn\u2019t turn out to be the perpetrator this time, it quite often has been in the past. What is it about this vegetable that makes it the stuff of bathroom nightmares? To discuss why lettuce and leafy greens are often spotted at the scene of foodborne crime, I spoke to Lee-Ann Jaykus, a food microbiologist with experience in many different organisms\u2014including nonculturable organisms, such as Cyclospora\u2014and a professor emerita at North Carolina State University. This conversation has been edited and condensed for clarity.<\/p>\n

Nadira Goffe: So why is lettuce one of the types of produce that always seem to come up in these conversations about foodborne illness?<\/strong><\/p>\n

Lee-Ann Jaykus:<\/strong> Foodborne pathogens are microorganisms that cause disease associated with the consumption of contaminated foods. There are three general categories of microorganisms that do this: There\u2019s the bacteria, which you hear about all the time, like Salmonella and E. coli. Then there are viruses, which includes my area of expertise, Norovirus. And then, the third category, which is what Cyclospora falls into, is something called parasitic protozoa. There really aren\u2019t very many of those that are associated with foodborne disease, though some are associated with waterborne disease, like Giardia.<\/p>\n

Cyclospora is a fairly newly discovered pathogen\u2014we\u2019ve recognized it for only about 25 years\u2014but unlike these other ones, it appears to be associated almost exclusively with the consumption of contaminated food, which is interesting because all these other things you can get from other mechanisms. So, immediately, if you start seeing Cyclospora cases pop up, you\u2019re going to say, \u201cOh, there must be some kind of food-contamination event going on.\u201d Over the years, we began to continually see outbreaks, and they almost always occurred in the summer months and were exclusively associated with produce items. Those items initially were berries; later on, we began to see them associated with herbs like cilantro or basil; over the years, that morphed into seeing them associated with leafy greens. There may have been other more specialty-crop types of outbreaks, but they\u2019ve been fairly small. But really, you should always, when you think of Cyclospora, think about fresh fruits and vegetables, ones that are eaten raw, not cooked. Because if you cook it, you\u2019re probably going to kill the parasite.<\/p>\n

So, when this popped up, we were like, Well, it\u2019s 99\u00a0percent certain it\u2019s associated with the consumption of the food, and those foods should fall into this category of these produce items that historically have been associated with the disease and are eaten raw. And which of those do we eat a lot of? Well, widely spread, the biggest is leafy greens. Everybody eats leafy greens. Not everybody eats cilantro, and even berries are a bit of a niche market. Of those, leafy greens are the most widely consumed and also the most widely distributed product.<\/p>\n

We still don\u2019t know the source of this summer\u2019s Cyclospora outbreak, but does the wide distribution of leafy greens, and lettuce in particular, make it more of a bear to deal with in regard to foodborne illnesses?<\/strong><\/p>\n

Every year, we have about 1,000 cases, and they\u2019re almost always associated with a particular product. But sometimes they can\u2019t figure out what that particular product is. When they have been able to find those specific products, in more recent years, it\u2019s almost always been either a specialty herb, like cilantro, or a leafy green. But usually, in the case of outbreaks, it is some kind of a combination product. Think about bagged salads. When you buy a bagged salad, you might have five different types of lettuce in there, some carrot pieces, some celery pieces, and so on. That\u2019s what we call a mixed product or a blend product. The other major category of product that\u2019s been associated with this has been vegetable trays.<\/p>\n

Mixtures like this can be one of the things that make it so hard to figure out exactly what product is causing it. By far, the most likely source of the contamination is during the growing phase\u2014or potentially the harvesting phase, if you were washing the produce. (But lettuce, for example, is usually not washed in the field, so, really, the growing phase.) Let\u2019s say you have five different leafy green types in a mixed salad or bagged salad. You don\u2019t know which of those leafy green products the contamination is associated with. It could be your red-leaf lettuce that is contaminated, but you take that red-leaf lettuce that has Cyclospora in it, then you mix it with all these other lettuces\u2014that\u2019s a process called commingling\u2014and you now have a shitload of contaminated product, for which going back and figuring out which of those lettuces was the culprit is really hard. And oftentimes, product is distributed not just to a single company but to many companies, or a product is what\u2019s called co-packed, so one manufacturing plant that\u2019s making bagged lettuce might produce for five different brands, like different big-box stores.<\/p>\n

When we came into this outbreak, I was relatively certain that the cause was more likely than not an herb or some kind of leafy green that\u2019s consumed raw. And as the outbreak has gotten bigger and bigger and bigger\u2014at this point, I think this will probably be the largest Cyclospora outbreak we\u2019ve ever had\u2014it\u2019s likely to be a very large lot of product that was contaminated and then distributed widely. So it\u2019s either a big bagged-produce supplier that distributes nationally or a big restaurant that\u2019s a national chain restaurant, let\u2019s say, that receives product centrally, then distributes it out to their restaurants.<\/p>\n

I can understand that leafy greens, and lettuce specifically, might be one of the biggest spreaders because of how widely they\u2019re distributed as a product that\u2019s eaten raw. But before all that, where does this parasite come from?<\/strong><\/p>\n

We don\u2019t know where this bug comes from.<\/p>\n

Like<\/strong> \u2026 at all?<\/strong><\/p>\n

Hardly at all. That is one of the things, from the standpoint of trying to prevent contamination from happening on a farm, we don\u2019t know much about. There are theories. Some people say it\u2019s a human-only contamination; another theory posits that certain reptiles carry it and it ends up getting on produce because you can\u2019t control animal encroachment in your growing fields. Maybe it gets into the water somehow and it happens <\/strong>because of irrigation. But we don\u2019t have an answer to that question.<\/p>\n

Without an answer, then, does anyone know why it\u2019s specifically berries, herbs, and leafy greens that get contaminated?<\/strong><\/p>\n

For leafy greens and cilantro, you would immediately think it\u2019s probably a water source. Maybe a wild animal source, but probably a water source. Berries are a little bit different, because the berries that have been associated with this are grown a little closer to the ground and they\u2019re not irrigated in the same way that lettuce or cilantro is irrigated. And so that\u2019s a bit of a mystery. It\u2019s hard to justify that it could just be a water source for berries.<\/p>\n

Now, I will say that in cases when they have been able to clearly link the food-product source of contamination, it\u2019s almost always a product that comes from Central or South America. Unless this current one is going to be a big surprise\u2014and it may be\u2014it doesn\u2019t tend to be a domestically produced product.<\/p>\n

That would make sense, why it\u2019s not zucchini or something.<\/strong><\/p>\n

Well, yeah, and there also are other reasons for that, some of them technical. For example, the surface of a fruit or a vegetable can be smooth, like a zucchini, or rough and have crevices, like lettuce or berries. And oftentimes you see contaminants\u2014it doesn\u2019t matter whether it\u2019s parasitic, protozoa, viruses, or bacteria\u2014cling to those cracks and crevices. It\u2019s also really hard to remove them, even with a water or chlorine-based wash. So there are other factors too as to why you might not necessarily see it in zucchini as you would in lettuce, for example.<\/p>\n

I was going to ask if the difficulty in cleaning these types of produce has anything to do with it. I read that even appropriately washing contaminated produce has <\/strong>varied results in how effectively it kills the parasite<\/strong><\/a>, none of them 100\u00a0percent. I understand that in life and science, there\u2019s never really\u00a0100 percent in anything, but is cooking it the next step to, if you got 90\u00a0percent of the contaminant off from washing it, killing maybe another 6\u00a0percent?<\/strong><\/p>\n

The bottom line is that if you were really concerned about your product, you would cook it. And I have friends (and I don\u2019t necessarily agree with them) who, when they make a fruit smoothie, will cook the fruit beforehand because they\u2019re concerned about minute chances of hepatitis A or Norovirus being in those. I think that their risk of getting those things from those products is minimal, but with that said, if you cook it, you will essentially eliminate an infectious parasite.<\/p>\n

An additional problem with Cyclospora is that we can\u2019t culture it in the lab. We can\u2019t really do studies where we figure out how easily it is inactivated, whether that\u2019s by heat, chlorine, ozone, or whatever. So we don\u2019t have a lot of data to back that up. But from what I know about these bugs in general, it\u2019s likely that if you cooked it, you wouldn\u2019t activate it. But who\u2019s going to cook lettuce?<\/p>\n

I imagine that the inability to culture Cyclospora makes it difficult to answer basic questions about it.<\/strong><\/p>\n

Norovirus is the same way: We really don\u2019t have a good cultivation method for Norovirus. That\u2019s been a huge impediment in understanding it from different perspectives, from the perspective of a food microbiologist, as well as that of a clinical microbiologist. Because if you can\u2019t culture it, you can\u2019t work with it. One of the problems with Cyclospora is that there are few people working on it, because the only way you can work with it is to get human poop that contains it. And then, even once you have that human poop and you can do things in the lab and try to figure out what\u2019s going on using fancy techniques, you still can\u2019t grow it.<\/p>\n

<\/p>\n

\"\"<\/p>\n

\n Gideon Meyerowitz-Katz
\n A Terrifying Food Label Is Spooking Even the Government. Just One Problem: It\u2019s Almost Meaningless.
\n Read More<\/b>\n <\/p>\n

<\/a><\/p>\n

Gosh, what an elusive, frustrating parasite.<\/strong><\/p>\n

It makes it super interesting, because our hands are tied. Parasitic protozoa tend to have different life stages. I think about it almost like a moth, which starts in a cocoon and goes through the pupal stage, et cetera. Oftentimes, Cyclospora falls into this category. It\u2019s only a certain phase in the life cycle of the parasite when it can infect humans. That makes it even more complicated to study because it\u2019s got to be in the right phase.<\/p>\n

So a big question is: Why is this seasonal? Well, maybe it\u2019s because, during the warmer or more humid months, it stays in the infectious phase longer, but who knows? And the genetics are very complicated. I have been told that there are many, many strains, not all of which infect humans, and they don\u2019t even know which strains infect humans.<\/p>\n

We\u2019ve talked about how tough it is to culture Cyclospora, how the nature of the parasite is hard to study. Is there anything else that makes it harder to get those answers?<\/strong><\/p>\n

To be honest, it\u2019s a pretty rare disease, and a lot of physicians, particularly community physicians, are not going to think about it, and they\u2019re not going to test for it. I mean, now they might, but it\u2019s a pretty specialized test that you need to do in order to diagnose it. So it\u2019s difficult to diagnose unless you have decided you\u2019re going to look for it. Additionally, the public health infrastructure in foodborne disease surveillance has been pretty decimated, and Cyclospora is one of the organisms that\u2019s been affected by that. [Due to this administration\u2019s gutting of the CDC earlier this year, the government agency reduced mandatory monitoring by the Foodborne Diseases Active Surveillance Network from eight germs to two<\/a>. Cyclospora is one of the pathogens that are no longer tracked.] So I think that we were late to the game because we don\u2019t have the resources and attention to this that we had even two or three years ago.<\/p>\n

Another complication is the process of figuring out the source of the outbreak, known as traceability. We have done a lot over the past 10 years to improve traceability in fresh produce, but it is far from perfect. It\u2019s hard to figure out the origin of a particular lot of a particular product, especially when you have the additional complicating factor of the incubation period. The way epidemiologists figure this out is they go to the patient and they do a food survey on that patient. Well, if you\u2019re asking someone what they ate for the past two and a half weeks, they\u2019re not necessarily going to remember, let alone the restaurant they ate it at or the brand that they ate or any of those kinds of things. So the investigation itself is tricky. This is a rapidly evolving situation that we don\u2019t have the answers for yet, but I will tell you, people are working as hard as they can to try to figure out what\u2019s going on with less resources, a difficult bug to study, and an imperfect set of circumstances.<\/p>\n

<\/p>\n

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