Cyclosporiasis: the science, risks and red flags

What’s small, round and could give you explosive diarrhea? Cyclospora parasites. The diarrheal disease they cause is wreaking havoc on thousands this summer in what is the largest known flare up in the U. S. ever. What’s causing it and what can we do about it? NPR’s Joseph Kim https://www.npr.org/people/g-s1-127759/joseph-kim joins host Nate Rott https://www.npr.org/people/348779465/nathan-rott to talk about the outbreak – and how to protect yourself and your loved ones. Read more of Joseph’s reporting on cyclosporiasis here https://www.npr.org/2026/07/12/nx-s1-5890935/cyclosporiasis-cyclospora-outbreak-diarrhea-states-us. Interested in more science in the news? Email us your question at [email protected] mailto:[email protected]. Support public media with NPR+ and enjoy perks for over 25 podcasts like this one. It includes perks like bonus episodes, early access, archive access, curated playlists and sponsor-free listening. Learn more at plus.npr.org http://plus.npr.org. See pcm.adswizz.com https://pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences. NPR Privacy Policy https://www.npr.org/about-npr/179878450/privacy-policy

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• 0:36Speaker 00

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• 0:41Speaker 01

  Hey there, Short Wavers. I don't know if you've heard, but there's this illness called cyclosporiosis that has been wreaking havoc on thousands of people across the US this summer as they've likely eaten contaminated produce. Joseph Kim is a science reporting fellow at NPR, and he has been following this story. And he's here to fill us in on all of the details. Hey, Joe.

• 1:03Speaker 02

  Hey, Nate.

• 1:04Speaker 01

  Help me out. What is cyclosporiosis?

• 1:07Speaker 02

  So cyclosporiosis is an intestinal infection caused by parasites of the genus Cyclospora.

• 1:12Speaker 01

  Okay.

• 1:13Speaker 02

  They look like the soccer balls we saw at the World Cup. And when they get inside people's digestive systems, people know. Because the symptoms that show up later include farting, abdominal cramping and watery, sometimes explosive diarrhea, it's pretty bad.

• 1:27Speaker 01

  Okay. Yeah, man, if I had any of those symptoms, I would definitely notice them. So that sounds awful.

• 1:34Speaker 02

  Yeah, does not sound fun. So I talked about it with Dr. Rebecca Wertz. She's a professor at the University of Minnesota School of Public Health and an infectious disease physician. She worked on the first known outbreak in the US in 1990 at Cook County Hospital's dormitory in Illinois.

• 1:50Speaker 03

  Doctors who were helping to staff the hospital, all within the space of a couple of days, getting sick with a serious diarrhea. And tests were done that showed no known cause of diarrhea. And it took some days, even weeks, for people to look then for a parasitic cause of diarrhea. And at that same time, those doctors were sick and they were unable to work that summer at the hospital. And all of them recovered, fortunately.

• 2:22Speaker 01

  Man, I'm glad to hear that they all recovered, but that sounds absolutely awful. How bad is the current situation we're experiencing, Joe?

• 2:30Speaker 02

  As of last week, 1,645 domestic cases have been confirmed by the CDC.

• 2:36Speaker 01

  Oh, wow.

• 2:36Speaker 02

  And they note they may have over 5,000 more cases they need to verify.

• 2:40Speaker 01

  Whoa.

• 2:41Speaker 02

  And Rebecca says we're in the middle of the largest known Cyclospora flare in the US ever.

• 2:47Speaker 01

  Oh, wow.

• 2:48Speaker 03

  And because we know that the confirmed cases are only the tip of the iceberg, I think we'll end up seeing many thousands of cases.

• 2:59Speaker 01

  Oof. Okay, so today on the show, what you need to know about these cases of explosive diarrhea breaking out across the country, and importantly, how you can avoid it. You're listening to Short Wave, the science podcast from NPR.

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• 4:37Speaker 01

  All right, Joe, so do we know what might be causing all of these cyclosporiosis cases?

• 4:42Speaker 02

  In a word, no. The FDA and CDC link cases from five states to lettuce served at Taco Bell. Taco Bell issued a statement July 16th that it took, quote, "immediate action to voluntarily remove potentially impacted lettuce from a supplier in select states." They also said in the statement that the lettuce would be removed from the supply chain nationwide and replaced within 24 hours. And so far, 34 states are reporting cases, so it doesn't account for all of them. We do know it's how it's been spread before. Because cyclosporiosis is actually seasonal.

• 5:17Speaker 01

  Oh, wow.

• 5:18Speaker 02

  There are cases every year, just not at the scale we're seeing right now. So we do know some things about it.

• 5:24Speaker 03

  It's spread in contaminated water. And so when someone ingests the water or food that's been washed with that water or grown with that contaminated water, they may ingest the parasite.

• 5:41Speaker 02

  In the 1990 outbreak, the culprit was drinking water at the resident's dormitory.

• 5:46Speaker 01

  Okay.

• 5:46Speaker 02

  Beyond that, the CDC notes that previous outbreaks are generally linked to fresh produce. In 2018, it was a salad at McDonald's. Raspberries, basil, cilantro, snow peas, and lettuce have all been culprits in the past, according to the FDA.

• 6:04Speaker 01

  Man, I'm picking up a pattern here. It's like these fast food restaurants. Nothing against fast food. I love it, but McDonald's, Taco Bell? Okay, so like, what can we do?

• 6:13Speaker 02

  Well, Nate, you want to make sure none of your produce has been recalled by checking the FDA website. And wash your hands with soap and water before handling your fruits and veggies. And make sure you wash your produce with uncontaminated water, even if the package says it's pre-washed. Vinegar and other popular chemical washes don't work, but cooking will kill it.

• 6:35Speaker 01

  So does this mean, Joe, that we should like, should stop eating fresh fruits and vegetables? Because my kid would love it if we paused the veggies. He never eats them anyway.

• 6:43Speaker 02

  Yeah, my brother, too.

• 6:44Speaker 01

  Yeah, we all have one.

• 6:46Speaker 02

  It depends on who you talk to. Rebecca Wertz, the doctor we heard from earlier, would say your kid is on to something, at least this one time.

• 6:54Speaker 03

  Until this has been sorted out, I think it's a reasonable plan to avoid eating salads and eating fresh produce. That includes both at home and in restaurants.

• 7:05Speaker 02

  But I talked to another physician, Kauzar Talat, who isn't as worried.

• 7:09Speaker 05

  Me personally, I am. We're still eating berries. We're still eating lettuce. We're still eating greens. I may have been a little lackadaisical about washing them in the past. I'm much more careful about making sure that I wash them and that every, every leaf of lettuce is washed well in running water.

• 7:25Speaker 02

  So Kauzar is an infectious disease doctor and an associate professor at the Johns Hopkins School of Public Health. And she says most healthy adults don't need to worry.

• 7:34Speaker 05

  The vast majority of people will have a self-limited infection, may never know that they were infected, or have a mild case of diarrhea that will go away by itself.

• 7:43Speaker 01

  All right, nice. So that means I can probably have my salads and, you know, still try to eat healthy. But now, like, I want to learn about what this bug actually is. Like, can I look at it in its eyes?

• 7:54Speaker 02

  So it's a small, round parasite.

• 7:57Speaker 01

  Okay.

• 7:57Speaker 02

  Only about the length of a red blood cell at its largest, or at least that's how they are usually. And no eyes. Sorry, Nate.

• 8:05Speaker 01

  Yeah, okay. So there's no eyes to stare menacingly into? That's a bummer, but, you know, okay, go on.

• 8:10Speaker 02

  Yeah, I know. And when they get into people's bodies, they invade cells in the small intestines, ravage through neighboring cells, then reproduce, and eventually end up in the toilet, hopefully, and not your pants, Nate.

• 8:24Speaker 01

  Yeah, well, I'm not going to tell you the story of the last time that happened, Joe, not on this podcast. But this whole thing is giving me the heebie-jeebies. Like, what's treatment like? Can we just kill this parasite if we have it with like an antibiotic or something?

• 8:38Speaker 02

  Yeah, this is what Rebecca says.

• 8:40Speaker 03

  There is one antibiotic that can be used, trimethoprim sulfamethoxazole. It's also called Bactrim or Sectra, which can be used to limit the symptoms, but that's not used as a routine. It's usually used in people who are a little bit more immunocompromised.

• 8:56Speaker 02

  And that's because their immune systems need a bit of extra help.

• 8:59Speaker 01

  Oh, that makes sense.

• 9:00Speaker 02

  Fun fact, Nate, this antibiotic also works for some other parasites. It works by blocking the bugs from making more DNA.

• 9:08Speaker 01

  Huh, yeah, I'm into that. Okay, so there are drugs available that work, but most people won't need them unless they're like really sick or immunocompromised.

• 9:18Speaker 02

  Yeah, exactly. Rebecca and Kauzar both say that young, old, and immunocompromised people should be extra cautious and proactive even about getting checked up if they're worried.

• 9:29Speaker 01

  Okay, so is that, you know, if I'm an immunocompromised person or I'm older, is that something that people should be looking out for, like bad diarrhea?

• 9:36Speaker 02

  Yeah, mostly bad diarrhea. A bad day on the toilet probably isn't something to be worried about, but, Kauzar says.

• 9:44Speaker 05

  If you, diarrhea persists for more than a couple, a few days, see your doctor. If the diarrhea goes away and comes back, that's another sign of potential Cyclospora infection. And again, go see your doctor.

• 9:57Speaker 02

  Again, for most people, this would show up as some bad trips to the bathroom. And CDC says it can be largely avoided by either limiting your veggie intake temporarily or else washing and cooking fresh produce thoroughly.

• 10:12Speaker 01

  But I mean, Joe, if this thing might just go away on its own, is it even worth going and seeing a doctor? I hate going to the doctor.

• 10:19Speaker 02

  Well, it's probably good just to confirm it's actually cyclosporiosis. And going to the doctor, reporting and getting tested, can also mean a lot for public health officials, helping them track down how many cases and possibly pin down the source faster. Also, PSA, if you're experiencing diarrhea, you should drink lots of water to replenish your fluids.

• 10:42Speaker 01

  So I guess what you're saying there, Joe, is that it's kind of like a civic duty to go to the doctor then?

• 10:46Speaker 02

  Yeah.

• 10:47Speaker 01

  Okay. And then getting treatment is just like a bonus, too?

• 10:50Speaker 02

  You bet. And we've covered a lot of ground in 10 minutes. So Nate, I want to leave you with some optimism. Rebecca says we can hope for a silver lining here.

• 10:59Speaker 03

  Hopefully, the source is identified in this outbreak and it's managed better in the future.

• 11:04Speaker 02

  Knowing exactly what's causing these cases nationally in so many states could mean that people can get a handle on a situation and hopefully at least get back down to a more regular case count, which is, you know, in the low hundreds instead of the thousands.

• 11:20Speaker 01

  Well, here's hoping for that, Joe. I, I, I hope that's what we end up at.

• 11:25Speaker 02

  Yeah, we can go back to our regular amount of diarrhea.

• 11:32Speaker 01

  Short Wavers, if you liked this episode, share it with your parasitic friends. You know who you are. Or your non-parasitic companions. Or you can share it with a buddy who's got an upset tummy and looking for answers. All of it helps our show. This episode was produced by Burley McCoy, edited by our showrunner Rebecca Ramirez, and fact-checked by Joe and Tyler Jones. The audio engineer was An Li Wong. I'm Nate Rot.

• 11:56Speaker 02

  And I'm Joseph Kim.

• 11:57Speaker 01

  Thanks for listening to Short Wave, the science podcast from NPR.

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