Parasitic infections likely linked to farming practices, not restaurants

By Rose Hoban

Cyclospora, a relatively unknown parasite, has been making headlines across the country as it’s given thousands of people an unpleasant case of explosive, watery diarrhea. In North Carolina, state leaders report there have been at least 307 cases of the infection. 

North Carolina Health News reached out to several experts here in North Carolina to get more context about the foodborne disease: State Veterinarian Carl Williams and infectious disease physician David Wohl from UNC Health. 

As of July 20, the Centers for Disease Control and Prevention lists a total of 5,100 suspected cases of Cyclospora nationwide. The CDC’s update page reads: “This is substantially higher than the 249 cases reported nationally by this same time last year.” The CDC’s numbers are likely an undercount, however, given that in an update dated July 20, the Michigan Department of Health and Human Services reports 6,148 cases in that state alone.

No deaths have been reported related to the outbreak. 

State Veterinarian Carl Williams told NC Health News that state health officials are updating case counts weekly. 

(Note: These interviews have been edited for length and conversational flow.) 

Carl Williams: We’re updating our case counts weekly, and our last update was 307 cases. But when we update our case count on Tuesday (July 21), it’ll go up from that.

NC Health News: At the end of last week, we heard that apparently this outbreak is being related to Taylor Farms lettuce. Do we think that is the only source, and the outbreak is related to the lettuce from that company?

Williams: What we suspect, based on previous years, is that there are multiple vehicles for Cyclospora beyond just the lettuce. And what we know is that the lettuce is what was implicated, especially in association with Taco Bell restaurants in the Midwest. 

The large outbreak in Michigan, Ohio and a couple other states did implicate lettuce with a trace back to Taylor Farms, but that’s not what we’re seeing in North Carolina or the other states. We’re seeing that it seems to be associated with a large number of products, and it’s really hard to nail down a specific one. 

Our best guess is that there’s probably multiple contaminated fresh fruits and vegetables that are contributing to this increase in cases that we’re seeing in North Carolina and across the country.

The U.S. Food and Drug Administration on Sunday withdrew its guidance about avoiding lettuce provided by Taylor Farms de Mexico, noting on its outbreak update website that, “Due to the complexity in detection of Cyclospora, FDA laboratory experts re-reviewed the sample results and have concluded that the finding does not represent true amplification and should be considered a false positive. Information about the sample has been removed from the July 18, 2026 update…  As of July 19, 2026, there are no confirmed positive sample results for product testing for Cyclospora.”

NCHN: Tell us a little bit about Cyclospora. I understand that it can be challenging to diagnose and then a little bit challenging to treat.

Williams: It’s a parasite, and it’s resistant to chlorine, and it’s hard to get off of fresh fruits and vegetables. 

Humans are the only known reservoir for it. There’s no animal component. The only reservoir is people, but it’s not transmitted directly from person to person. Once the oocysts (spores) are shed in the feces, it takes up to a week for them to become infective. So it has to hang around in the environment and attach to a food product. It’s not going to be something like Shigella that’s directly transmissible from person to person. 

What we’ve noticed in North Carolina and the United States is that it’s really a summertime phenomenon. We see almost all of our cases in June and July, with very few outside of that window.

NCHN: So this is, what, someone pooping in a field? And then somehow or another, the lettuce gets contaminated with that soil. Is that what you’re telling us?

Williams: It could be that. But in the past, outbreaks have been traced to surface water being contaminated with human feces, and then that water being used to either irrigate crops or to apply pesticides. So then, you can get, as opposed to just imagining an individual person having a bowel movement that might affect a very small area of a field. But if it’s being sprayed across the entire field for irrigation, that is how, or one way, that it could be placed on all of these fruits and vegetables. 

The FDA has a lot of good information on their website for farmers and producers.

It’s very important where these fruits and vegetables are grown that the farmers adhere to good practices for septic systems, septic field placements, as well as using clean surface water for irrigation and pesticides and things like that, because these are all ways that the product could become contaminated at the source. 

I think that’s an important distinction because restaurants [associated with the outbreak] aren’t really doing anything wrong. They’re getting product that’s contaminated, but they obviously don’t know it. You can’t see it, and unlike ground beef or chicken, which we cook to kill pathogens, there’s generally no “kill step” for fresh fruits and vegetables. Your tomatoes are served raw, they’re sliced up and put on the hamburger. The hamburger is safe because it’s been cooked, but the tomato, it’s not going to be cooked, right? Or the cilantro, or the parsley, or whatever it is. 

That’s one of the reasons that it gets really tricky to figure out what specifically is associated with transmitting Cyclospora.

NCHN: When you have a bacterial outbreak, you can do DNA testing and maybe identify the source, but I understand that’s harder to do with Cyclospora. Why is that?

Williams: In North Carolina and in most states, we can do whole-genome sequencing for things like Shiga toxin producing E. coli or salmonella right at our state public health laboratory. But Cyclospora, because it’s a parasite, number one, it has a much larger genome, so there’s a lot more genetic material to go through and only the CDC does it. Everything needs to be shipped to the CDC, but they can do the molecular analysis and they can identify clusters for us based on genetically relatedness. It just takes longer. 

What we’ve heard from the CDC is that this year, in particular, their lab is overwhelmed, and they’re probably going to implement some type of a strategy to prioritize cases for sequencing. But they’ve not specifically told us yet. All the states have a weekly call with them [on Mondays] so they might tell us more.

NCHN: Is it correct that the CDC stopped tracking Cyclospora last year?

Williams: It’s been reportable in North Carolina for years, and it’s been notifiable to the CDC. It’s still something we have always reported to the CDC.

The CDC website notes that reporting on Cyclospora by states became optional in 2025. Previously, reporting on Cyclospora had been required since 1997. Multiple media outlets reported last year that the federal agency has cut back on foodborne illness surveillance. 

Reporting infections with Cyclospora is still required in North Carolina. 

Since Cyclospora has no animal carriers, we reached out to David Wohl, an infectious disease physician at UNC Health, to ask about treatment and prevention in humans. 

NCHN: What people really want to know is how they should treat this thing if they get it. Have you seen any cases of cyclosporiasis at the hospital? 

David Wohl: There have been cases at UNC Health, and, as you know, it’s not something that’s always routinely tested for. It’s probably just a tip of the iceberg, because you know there could be cases of diarrhea that either don’t come to the doctors’ attention or are not even tested for. 

We’re definitely seeing some cases over the last couple of weeks. 

NCHN: Is that unusual?

Wohl: Yes. We usually don’t test for it, but, like, once you start, there’s a little bit of a phenomenon where now people are sensitized to it. So we will be testing specifically for it. 

The commercial laboratories were picking up on this in May before this was even reported, on some of their panels that happened to include Cyclospora, so it wasn’t like Cyclospora was … suspect, but it happened to be on a panel that someone happened to order, even though they weren’t looking for it. So sort of an indicator, a bellwether that it was picking up even before the official cases. Now that there’s official cases and all the news, now people, clinicians like me, are more likely to tick the box for this test, where some of the panels we get don’t include it.

NCHN: It’s a little bit of a vicious cycle, where if you look, you find it?

Wohl: Yes, but it’s still concerning. Now, you know, there’s a lot of other GI pathogens that happen all the time that are even more likely. We still see dysentery, but this is different, and, like, there may be a specific source.

This is coming from somewhere, and as we know, cases can spread to other people, right? So we know that if someone has Cyclospora, they can spread it to others. So even though it may have started with one source or three sources, now the source can be other people. 

It is fecally transmitted, and so you do worry that there could be cases that are transmitted person to person. That would be the only concern that I have. This is mostly where people get this from, like, irrigation of fields with night soil kind of things, or people pooping in the fields because there are not good sanitary places to go to the bathroom. 

NCHN: I understand that Bactrim is the drug of choice, but there a lot of people are allergic to Bactrim. What should they do for treatment?

Wohl: There are some choices for people who can’t tolerate sulfide drugs. Bactrim is a sulfide drug, so if you’re restricted from sulfide, this would not be for you.

There is a drug called nitazoxanide that we’ve used for people who have sulfur allergy, and in some case reports has been found to be effective. There’s some evidence that Cipro, a common antibiotic, or Azithro, another common antibiotic, can also work. 

But remember, in a lot of people who are not immunocompromised, this can be self-limiting. If you have a more mild illness, you may not need medication, but I can understand why people would want to get treated if you have any symptoms at all.

NCHN: You can get over your case of Cyclospora without an antibiotic? 

Wohl: Yes, it can be self-limiting.

NCHN: What happens in the meantime? 

Wohl: For people who have a normal immune system, it’s variable, but this can just go on for a couple of weeks and then get better. And I think there’s a lot of people who do get infected who do not know it — here and worldwide. 

The problem really is people whose immune systems are weaker.

NCHN:  Is there anything we missed?

Wohl: I’m surprised you didn’t ask about, like, if this is a reflection of the breakdown of our public health system.

NCHN: Is it? 

Wohl: We have too few people working on lots and lots of different issues at the same time, whether it be Ebola, previous to that hantavirus, and now Cyclospora.

You need a deep bench of people, and so again I can’t imagine that we’re in any better position at state levels or federal levels to handle something like this in the wake of cuts.

So it’s really concerning. I’m not saying “oh, well, the cuts led to this.” I’m just saying our ability to respond to multiple threats at once is compromised, and that’s what I think people have to realize is that it’s not waste or fraud to have a deep bench of people who can keep us safe.

NCHN: So, Dr. Williams, what should people be doing with their produce to keep themselves from acquiring an infection? 

Carl Williams: We’ve always encouraged people to wash their fresh fruits and produce, and that’s still good advice. I think the key thing is it’s not a guarantee that this parasite will be eliminated. 

The other thing is, too, just there’s a bit of perspective. I mean, we have 300 cases in a state with 11 million people. We have, every year, about 3,000 cases of Salmonella and 3,000 cases of Campylobacter. Most people probably aren’t going to become infected with Cyclospora. 

I don’t want to say something like don’t eat fresh fruits and vegetables or cook all of them to 158 degrees Fahrenheit. You certainly could do that, and that will kill Cyclospora. But I think you know you just need to try and be cautious and wash your fruits and vegetables. That’s the best thing we can say, really.

NCHN: What’s the best way to do that? Soap and water? Disinfectant drops?

Williams: I think it’s more mechanical action. Cyclospora oocysts are resistant to chlorine, right? So if you use chlorine as a common disinfectant … it won’t work with Cyclospora. 

I think washing is a key thing. Outbreaks in the past have been associated with things like raspberries, where, well, you can look at a raspberry. It’s very hard to wash them because there’s all these crevices where things can hide, and you … just do the best you can with that.

That probably sounds unsatisfying, but you know, I’m still eating raspberries because I like them. I suppose that you’re rolling the dice a little bit. But I suspect, given the numbers of raspberries that are sold in the state that, odds are, most of them are fine.

NCHN: Is there something in particular that folks should maybe approach with a little more caution, like parsley or cilantro?

Williams: Those items do stick out most frequently when we ask people about what they have eaten and do what’s called the ingredient level analysis: parsley and cilantro, they do pop out. I suppose one option would be to just not have those, just forgo those — not for the entire year, but just during the season, which typically runs through the end of this month.

NCHN: So more caution during the summertime.

Williams: Definitely. And the other thing we like to remind people is don’t forget to cook your hamburgers. I mean, there’s still the classic pathogens that are out there, and your chicken and your pork and all of that stuff, because it’s not just Cyclo that makes people sick.

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