Cyclosporiasis: the science, risks and red flags

Summary

Podcast Summary: Short Wave (NPR) — "Why Explosive Diarrhea is Breaking Out Across the U.S.: The Cyclospora Outbreak"
Date: July 21, 2026
Hosts: Nate Rott, Joseph Kim
Guests: Dr. Rebecca Wirtz (University of Minnesota), Dr. Kawazar Talat (Johns Hopkins School of Public Health)

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Episode Overview

This fast-paced, science-for-everyone episode investigates the U.S.'s largest cyclosporiasis outbreak to date—an intestinal illness caused by a microscopic parasite. Hosts Nate and Joseph break down the science behind the sudden surge in reported cases, explore how the infection is spread (and why lettuce from Taco Bell is getting attention), and offer practical tips for protecting yourself, all while keeping the vibe light and accessible.

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Key Discussion Points and Insights

1. What is Cyclosporiasis?

• Definition: An intestinal infection caused by the Cyclospora parasite.

• Symptoms: Notable for flatulence, abdominal cramping, and "watery, sometimes explosive diarrhea."

  • Joseph Kim: "[Symptoms] include farting, abdominal cramping, and watery, sometimes explosive diarrhea. It's pretty bad." (01:12)

• Historical context: First U.S. outbreak in 1990 affected hospital staff; doctors were sickened and unable to work for weeks.

  • Dr. Rebecca Wirtz: "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..." (01:50)

2. How Big is the Outbreak Right Now?

• CDC Numbers:
  • 1,645 confirmed domestic cases (as of episode air date)
  • Over 5,000 additional suspected cases pending verification (02:29)
• Dr. Wirtz: "We’re in the middle of the largest known cyclospora flare up in the US ever... confirmed cases are only the tip of the iceberg..." (02:47)

3. Where Is It Coming From? What’s the Source?

• Current Theories:
  • The FDA/CDC have linked some cases to lettuce served at Taco Bell (five states implicated). Indeed, Taco Bell voluntarily pulled lettuce from its supply chain.
  • However, 34 states are reporting cases, so the situation is broader.
  • Outbreaks are seasonal and historically tied to contaminated water or fresh produce.
• Previous produce linked: McDonald's salads (2018), raspberries, basil, cilantro, snow peas, and other lettuces.
  • Joseph Kim: "We do know some things about it... It's spread in contaminated water." (05:00)
• Dr. Wirtz: "It's spread in contaminated water... food that's been washed with that water..." (05:00)

4. How Can You Protect Yourself?

• Prevention Advice:
  • Check for produce recalls on the FDA site.
  • Wash hands well with soap and water before handling food.
  • Wash all produce thoroughly—even “pre-washed” packaged products—using clean water only.
  • Vinegar and popular chemical washes do not work.
  • Cooking produce will kill the parasite.
• To Eat or Not to Eat Fresh Produce?
  • Dr. Wirtz (Cautious): "Avoid eating salads and fresh produce... at home and in restaurants until this has been sorted out." (06:29)
  • Dr. Kawazar (Moderate): "We're still eating berries... lettuce... just much more careful about washing them. Every leaf of lettuce is washed well in running water." (06:44)

5. Who Is Most at Risk, and When Should You See a Doctor?

• Symptoms: Mostly limited to digestive upset in healthy adults.
  • Dr. Kawazar: "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." (07:09)
• At Risk: Children, elderly, and immunocompromised people should be especially vigilant.
• When to Seek Medical Care:
  • If diarrhea lasts several days or clears and returns, see a doctor.
    • Dr. Kawazar: "If your diarrhea persists for more than a few days, see your doctor. If the diarrhea goes away and comes back, that's another sign..." (09:18)
• Treatment:
  • There is an antibiotic (Bactrim/Septra), used mostly for the immunocompromised.
  • Dr. Wirtz: "Not used as a routine—usually used in people who are a little bit more immunocompromised..." (08:15)
• Joseph Kim: "...But most people won't need them unless they're, like, really sick or immunocompromised." (08:43)

6. Why Reporting Matters

• Even if healthy people might recover on their own, reporting suspected cases helps public health officials track the outbreak and potentially pinpoint sources.
  • Joseph Kim: "...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." (09:54)

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Notable Quotes & Memorable Moments

• "They look like the soccer balls we saw at the World Cup... symptoms include farting, abdominal cramping, and watery, sometimes explosive diarrhea."
  • Joseph Kim (01:12)
• "We’re in the middle of the largest known cyclospora flare up in the US ever... confirmed cases are only the tip of the iceberg."
  • Dr. Rebecca Wirtz (02:47)
• "Vinegar and other popular chemical washes don’t work, but cooking will kill it."
  • Joseph Kim (05:48)
• "We're still eating berries. We're still eating lettuce. ...I'm much more careful about making sure that I wash them. Every leaf of lettuce is washed well in running water."
  • Dr. Kawazar Talat (06:44)
• "If your diarrhea persists for more than a few days, see your doctor. If the diarrhea goes away and comes back, that's another sign..."
  • Dr. Kawazar Talat (09:18)
• "Knowing exactly what's causing these cases nationally in so many states could mean that people can get a handle on the situation..."
  • Joseph Kim (10:39)
• Humorous/Light Moment:
  • Nate Rott: "Well, here's hoping for that, Joe. I hope that's what we end up at."
  • Joseph Kim: "Yeah, we can go back to our regular amount of diarrhea." (11:00–11:07)

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Timestamps for Important Segments

• [01:03] — Defining cyclosporiasis and symptoms
• [02:29] — Scope of the outbreak; current case counts
• [04:17] — Discussion of possible sources and current produce recalls
• [05:00] — How it's spread (water, produce), and historic outbreaks
• [05:48] — How to wash and handle fresh produce
• [06:29] — Differing opinions on whether to eat fresh produce during outbreak
• [08:15] — Discussion of treatments and who’s at risk
• [09:18] — When to seek medical attention
• [09:54] — The importance of case reporting for public health
• [10:39] — Optimism for future control if the source is identified

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Summary Takeaways

• The U.S. is seeing an unprecedented surge in cyclosporiasis, a diarrheal illness caused mainly by eating contaminated produce, notably lettuce this year.
• Main defense: stay alert for recalls, wash produce thoroughly, and avoid uncooked greens if particularly vulnerable.
• For most healthy people, symptoms are mild and self-limited—but reporting suspected cases is important for outbreak tracking.
• The outlook is hopeful: with source identification and better management, case numbers should fall.

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Short, Final Message:
Stay informed, stay vigilant with your veggies, and if in doubt—wash, cook, and when necessary, report symptoms to your doctor. "We can go back to our regular amount of diarrhea"... soon, hopefully.

Transcript

[Narrator/Announcer]

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[Nate]

Hey, Nate, Rod here with an ask for you casual listeners out there. Can we invest more in this friendship? We both like each other. Why not? We'd love if that could happen, but only you have the power to do that by clicking to follow Shortwave in your podcast app. That way you'll never miss the show, which is starting right now.

[Narrator/Announcer]

You're listening to Shortwave from npr.

[Nate]

Hey there, short wavers. I don't know if you've heard, but there's this illness called cyclospiriasis. It 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.

[Joseph Kim]

Hey, Nate.

[Nate]

Help me out. What is cyclospirasis?

[Joseph Kim]

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

[Nate]

Okay.

[Joseph Kim]

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.

[Nate]

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

[Joseph Kim]

Yeah. Does that sound fun? So I talked About it with Dr. Rebecca Wirtz. 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.

[Dr. Rebecca Wirtz]

Doctors who were helping to staff the hospital all within the space of a couple 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.

[Nate]

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?

[Joseph Kim]

As of last week, 1645 domestic cases have been confirmed by the CDC.

[Nate]

Oh, wow.

[Joseph Kim]

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

[Nate]

Whoa.

[Joseph Kim]

And Rebecca says we're in the middle of the largest known cyclospora flare up in the US Ever.

[Nate]

Oh, wow.

[Dr. Rebecca Wirtz]

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.

[Nate]

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 Shortwave, the science podcast from npr.

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[Nate]

we know what might be causing all of these cyclospirasis cases?

[Joseph Kim]

In a word, no. The FDA and CDC linked cases from five states to let us serve the Taco Bell. Taco Bell issued a statement July 16 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 cyclosporiasis is actually seasonal.

[Nate]

Oh, wow.

[Joseph Kim]

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

[Dr. Rebecca Wirtz]

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.

[Joseph Kim]

In the 1990 outbreak, the culprit was drinking water at the residents dormitory.

[Nate]

Okay.

[Joseph Kim]

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.

[Nate]

Man, I'm picking up a pattern here. It's like these fast food restaurants. Nothing against fast food.

[Joseph Kim]

I love it.

[Nate]

But McDonald's, Taco Bell. Okay, so, like, what can we do?

[Joseph Kim]

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.

[Nate]

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

[Joseph Kim]

Yeah, my brother too.

[Nate]

Yeah, we all have one.

[Joseph Kim]

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

[Dr. Rebecca Wirtz]

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.

[Joseph Kim]

But I talked to another physician. Cows are talat. Who isn't as worried?

[Dr. Kawazar]

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. Every leaf of lettuce is washed well in running water.

[Joseph Kim]

So Kawazar 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.

[Dr. Kawazar]

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. And that will go away by itself.

[Nate]

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

[Joseph Kim]

So it's a small, round parasite, okay. 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.

[Nate]

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

[Joseph Kim]

No. 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.

[Nate]

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?

[Joseph Kim]

Yeah, this is what Rebecca says.

[Dr. Rebecca Wirtz]

There is one antibiotic that can be used. Trimethoprim sulfamethoxisole. It's also called Bactrim or Septra, 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, and that's

[Joseph Kim]

because their immune systems need a bit of extra help.

[Nate]

Oh, that makes sense.

[Joseph Kim]

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

[Nate]

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.

[Joseph Kim]

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.

[Nate]

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, back bad diarrhea?

[Joseph Kim]

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

[Dr. Kawazar]

Kawazar says if your diarrhea persists for more than 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 again.

[Joseph Kim]

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.

[Nate]

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.

[Joseph Kim]

Well, it's probably good just to confirm it's actually cyclosporiasis 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.

[Nate]

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.

[Joseph Kim]

Yeah.

[Nate]

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

[Joseph Kim]

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.

[Dr. Rebecca Wirtz]

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

[Joseph Kim]

Knowing exactly what's causing these cases nationally in so many states could mean that people can get a handle on the 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.

[Nate]

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

[Joseph Kim]

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

[Nate]

shortwavers. If you like 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.

[Joseph Kim]

And I'm Joseph Kim.

[Nate]

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

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