The Explosive Diarrhea Outbreak Is About to Get Much Bigger

The US’s explosive diarrhea problem is worse than you think—and it’s about to get even messier.

The country is grappling with a large and fast-spreading outbreak of cyclosporiasis, a parasitic infection that causes extreme gastrointestinal distress. There are nearly 7,000 potential cases, more than 3,300 of which are in Michigan alone as of Tuesday, and state officials have identified tainted lettuce as the likely culprit.

The actual case count is almost certainly higher, though, because most people don’t seek medical care when they get diarrhea. And even when they do, labs don’t routinely test for cyclosporiasis, says Jeanne Marrazzo, CEO of Infectious Diseases Society of America. She estimates cases are at least double the Centers for Disease Control and Prevention’s numbers.

“That’s because of underdiagnosis and also because there are cases that are likely to be mild. Many people aren’t going to declare themselves and get counted,” she says. Cyclosporiasis isn’t as common as other foodborne illnesses, meaning it’s not included in standard panels that test for several types of gastrointestinal disease.

But for many folks who get sick, the effects are, let’s just say, not pleasant. “A lot of times with diarrhea, you have an episode and you feel better,” says Marrazzo. “With this, it just can kind of go on and on, and it really takes people out.”

Bad enough, yes. But about that whole getting worse thing.

Public health officials have urged people to thoroughly clean produce, and some restaurants have taken precautions. Notably, Taco Bell has said it had “voluntarily and temporarily removed limited ingredients at select restaurants as a precautionary measure.” While that might help those trying to live mas avoid getting cyclosporiasis, it’s not the only part of the produce supply chain that can be affected.

Norman Beatty, associate professor of medicine in the division of infectious diseases and global medicine at the University of Florida, says the cyclospora parasite has unique mechanisms that allow it to lodge into the crevices of other fruits and vegetables. It’s most commonly found in fresh, raw produce, particularly herbs, lettuce, and berries.

Unlike some of the more common foodborne pathogens, cyclospora is resistant to bleach and common sanitizers used by food manufacturers. “Despite the commercial approaches to washing the produce that ends up in our grocery stores, the oocysts can continue to stick,” says Beatty. (Oocysts are the infectious stage of the parasite.)

Cooking destroys the parasite, but because lettuce and berries are usually eaten raw, there’s no easy way to eliminate it before consumption.

Bill Marler, a lawyer who specializes in food poisoning cases, says that, historically, most cyclosporiasis cases have been linked to imported produce. But the last decade has seen the US’s first All-American cyclospora outbreaks, such as when bagged lettuce from a plant in Illinois sickened more than 700 people.

Marler described cyclospora as becoming “like pythons in the Everglades.” The invasive snakes have infamously taken over the wetlands of South Florida, outcompeting native fauna and inspiring a year-round python hunting season. Cyclospora threatens to do the same, using our guts as the host environment. As more people get cyclospora and poop it out, it becomes more likely that water gets infected. That in turn increases the risk of outbreaks.

“Likely what happens is, it gets into the water supply that’s utilized to irrigate crops,” Marler says. He adds that agricultural workers typically get blamed for outbreaks, but “this is unlikely to be one lone worker not washing his or her hands, or someone pooping in the field. Something has gotten a water supply contaminated, spreading over a larger amount of produce.”

The parasite is also resistant to chlorine, the primary disinfectant used in most municipal water and wastewater treatment systems.

Beatty says it’s likely that thousands more people around the country have been infected.

“This shows us how easily an organism can be distributed to one location within the United States to multiple locations pretty quickly through the networks that we have set up for food distribution,” he says. “This could end up being reported in all 50 states.”