Science Friday - Hold the lettuce: Updates on the 'explosive' cyclospora outbreak

Episode Date: July 17, 2026

An outbreak of the foodborne illness cyclosporiasis has sent thousands of people running to the bathroom this summer. Health officials have linked the outbreak to lettuce served at Taco Bell locations in five states, but there are still a lot of unanswered questions. Food safety expert Byron Chaves joins Flora to talk about the “explosive” nature of the illness and why pinpointing a source of the parasite has been so difficult. Guest: Dr. Byron Chaves is an associate extension specialist and professor in the Department of Food Science at Rutgers University in New Jersey.  Transcripts for each episode are available within 1-3 days at sciencefriday.com. Subscribe to this podcast. Follow our show on Instagram, TikTok, Facebook, and Bluesky @scifri and sign up for our newsletters. Got a science question that’s keeping you up at night? Call us: 877-472-4374 Hosted by Simplecast, an AdsWizz company. See pcm.adswizz.com for information about our collection and use of personal data for advertising.

Hey, I'm Flora Lickman, and you're listening to Science Friday. Step away from the Taco Bell CrunchRap Supreme, says the FDA. An outbreak of foodborne illness caused by the parasite cyclospora has been cropping up across the country, sickening thousands. And after months of trying to track down the source, investigators have linked some cases to shredded iceberg lettuce supplied to Taco Bells in five states, Indiana, Kentucky, Michigan, Ohio, and West Virginia. The Washington Post broke the story and linked the lettuce to one company, Taylor Farms.

Here to give us the latest on this investigation and to take us into the world of food detective work is Byron Chavez, a food safety expert from Rutgers University. Hey, Byron, welcome back to Science Friday. Hey, happy to be here. Thanks for the invite. Thank you for coming. You know, thousands of people have gotten sick. many of the rest of us have been wondering what not to eat this summer. I feel like this has been a real nail biter. Has the cyclospora mystery been solved?

So not quite yet. We actually have today probably more questions that we did yesterday. Oh, say more. Tell me. Well, with this new development that lettuce might be implicated, then we have a number of other questions about how did contamination happen. Is this really a single source? Is potentially tackle bell the only retail chain that it's involved is any of these lettuce in the market right now? Right, because, you know, I know that the states called out by the FDA and CDC didn't include, for example, New York where there have been a bunch of cases.

So what does that mean? Yeah, it probably means what we've been thinking about for the last couple of months, almost. it seems like this outbreak has been lingering for forever. But there's actually more than one outbreak happening at the same time, right? So we finally have a lead about a proportion of the cases that might be associated with consumption of contaminated lettuce. But that doesn't mean that there are not other outbreaks happening simultaneously. And like you mentioned, there's five states associated with the lettuce one. But there's many other states.

There's 34 states where people have. reported getting sick, including New York. And so there might be a series of outbreaks happen. So news outlets have been pointing to Taylor Farms. Does that suggest that the parasite came from processing or from the farm itself? You know, I would be cautious about pointing towards a specific source right now because, you know, as a Friday morning, I think it's too early to tell exactly where this is going from. Now, what I would say is that cyclospora, it's not what we would typically call an environmental organism in food processing, right? So when the lettuce is getting shredded in a food facility and mix with a lot of other lettuce coming from different places, it's not like this microbe is surviving in the processing environment.

What is more likely to happen is that the microbe already came with the heads of lettuce that were introduced into processing facilities. So think about lettuce that got irrigated with contaminated water and stuff like that. So the more likely cause of direct contamination is irrigation water. Why has it taken so long to figure this out? Yeah. You know, epidemiologists are working really, really hard to figure that out themselves. I think that, again, there's this hypothesis that there's a series of outbreaks that are happening at the same time.

And while some of the cases may be attributed to consumption of contaminated lettuce, there could be other cases associated with either recreational water or potentially other foods that are happening across the country. Recreational water, do you think it's a possibility that people are getting it from swimming? I think that there's multiple hypotheses. And recreational waters, despite what the Michigan Department of Health and Human Services is saying, has been implicated in outbreaks of cyclosporiasis, and there's evidence, documented evidence

from other places in the world. Maybe there's untreated wastewater or semi-treated wastewater that ended up in recreational lakes and such. And because we're seeing so many thousands of cases that it is a possibility that recreational waters could have contributed to some of those cases. Now, the other thing that we have seen, is there's no reported cases in Canada, right?

And so I do wonder, you know, what's happening across the lakes when people in Detroit and other places in the country here are getting sick and no Canadians are getting sick, right? So that will also give us a little bit of a hint as to what foods were distributed in the U.S. that were not potentially distributed to Canada, and we can potentially start narrowing this time. So we've talked on this show about budget.

and staffing cuts at various government agencies. Do you believe that those played a big part in this outbreak being so big? You know, I would also be cautious about that. I think that by the loss of life, the outbreaks, outbreak or outbreaks would have happened anyway, right? I think that what we are missing here is a little bit of connection between the CDC and other federal agencies and state governments. every time that we make cuts to public health infrastructure, there's going to be a consequence, right?

And the consequence here was probably that the response could have been faster, but certainly the outbreak would have happened anyway. Tell me a little bit about the parasite itself. I mean, I've heard that it can cause problems for weeks. Someone had symptoms for 100 days. Is it exceptionally hardy? Yeah, you know, parasites are one of those things that in general we're terrified of, right, because of the way that these things, these organisms have been portrayed in the media. And there's some reality to that.

Now, the truth about cyclospora is that as scientists and microbiologists, we still don't understand a lot of the infectious cycle, the biology of this organism, and the detection methods that we have may not be the most adequate. And so certainly we have a lack of scientific resources in that regard. What we do know is that this is not a person-to-person transmission, right? So we know that the infectious cycle happens in a variety of stages. And when people have cyclosporiasis and they shed the parasite in their feces, that parasite that comes out, it's not immediately infectious.

It needs some time in the environment at the right temperature and the right relative humidity, contaminating water or produce so that then people will consume that water or produce and get sick themselves. So it is an interesting life cycle. I mean, explosive diarrhea has been the cyclospora catchphrase. Is that scientifically real? Explosive diarrhea, it's not really a clinical term, right? So it is an interesting term. But what we mean by explosive diarrhea is that a proportion of the cases will have gas, right?

We'll have a lot of gas accumulated in their bowels. And then this basically makes you have a very loud, aka explosive bowel movement. But the diarrhea will be, we describe that as watering diarrhea. That is a better term for that. Why does bagged salad so often seem to be a culprit in these food safety stories? Yeah, that is a phenomenal question and a phenomenal mystery as well. Now, you know, bagged salads is a product of convenience and a product of we want produce year-round and we want accessibility to things. And that is great.

Now, when we bring any raw agricultural commodity from a farm into a processing operation, there is a chance that that raw agricultural commodity like lettuce may be contaminated with something, right? There's obviously on-farm food safety practices that are followed, but there's always chances. Now, one of the things that happens here is that hundreds of heads of lettuce are being mixed and cut and chopped. and place into packages, right? So we have a variety of heads of lettuce that come from either a single source or multiple farms, increasing the chances that there could be cross-contamination, right? So even if only a proportion of the lettuce that came into that process and operation is contaminated, then when we chop it and mix it, then everything is just going to be contaminated.

You're a food safety expert. Is there some kind of magic technology? in the pipeline or process that would prevent outbreaks like this? You know, if I had an answer for that, I wouldn't be a culture professor. I would be a billionaire. But I think, you know, people are working really, really hard on finding alternatives for what we currently have. Now, what we currently have is things like chlorine, right, chlorinated water where produce is immersed. but that is not effective for pathogens like cyclospora.

It is effective for things like E. coli and salmonella, right, which are bacterial foodborne pathogens. But cyclospora is a very hardy organism when we find it in the environment. It's in this porolated oocyte that is extremely resistant, right? So we are finding other ways, you know, for water, there are technologies like microfiltration and reverse osmoses. but those are expensive, right? So it's not always, it's not always available. Okay, given current info, what are you going to avoid at the supermarket?

That is a great question. And, you know, I'm not in the business of telling people what not to eat, but the way that I'm going to save my, you know, that I'm going to save myself and my soul is by saying that I do consume produce, but I don't typically eat salads. And so the produce that I consume at home is just typically cooked or stuff like that. I have never really been a big fan of leafy greens myself except for spinach. And then I eat it cooked at home.

So that's the way that I'm saying. Cook your food. That's what I'm hearing. That's what I'm hearing from you, Byron. Totally. But, you know, we don't want to cook cilantro, right? I mean, what kind of experience would we have? But, you know, keep an eye on the news, right?

Once the sources are confirmed, we will have, of course, more certainty. But if you do want to cook your produce, then 158 degrees would like to kill the parasite. There you go, 158 degrees. Byron Chavez is an associate extension specialist and professor in the Department of Food Science at Rutgers University in New Jersey. Thanks for joining me today. Thanks for having me. This segment was produced by Annette Heist and Charles Berkowitz. Do us a solid rate and review the show.

And number two, tell your friends about us. Thanks for listening. I'm Flor Lichten.