A Diarrhea-Causing Parasite Is Spreading Across 31 States, and No One Knows the Source Yet

An intestinal parasite is working its way across the country, and health officials still can’t say where it’s coming from. The CDC has logged more than 840 confirmed cases of cyclosporiasis across 31 states since May, and Michigan alone has topped 1,500 cases, the largest outbreak of its kind in state history.

The parasite is called Cyclospora, and the illness it causes is not the kind of thing you shake off in a day.

What Cyclospora actually does to you

Cyclospora is a microscopic parasite you can’t see, taste, or smell on food. Once it’s inside you, it causes cyclosporiasis, and the main symptom is watery diarrhea that can drag on for weeks if it goes untreated.

The rest of the package is rough too: stomach cramps, nausea, loss of appetite, and a deep fatigue. The incubation period runs about seven to 10 days after exposure, so by the time people feel sick, they often can’t remember what they ate that did it.

As of the latest CDC count, there have been more than 80 hospitalizations nationwide and no reported deaths.

Michigan is the epicenter

No state has been hit harder than Michigan. The Michigan Department of Health and Human Services has reported more than 1,500 cases, calling it the largest cyclosporiasis outbreak the state has ever recorded.

The cases have clustered in the southeast part of the state, across counties including Monroe, Lenawee, Washtenaw, Wayne, and Oakland. State health officials have been pushing food-safety guidance while they wait for the source to be identified.

The source is still a mystery

Here’s the frustrating part. Despite hundreds of cases across dozens of states, no FDA or CDC advisory has named a specific food, farm, brand, or store as the culprit. The investigation is still open.

What officials do know is history. Past US cyclosporiasis outbreaks have been traced to fresh produce: raspberries, basil, cilantro, snow peas, and lettuce, along with bagged salad mixes and pre-cut blends. The parasite spreads when food or water gets contaminated, usually somewhere along the growing and handling chain.

The timing is awkward too. The outbreak is unfolding as the CDC deals with workforce cuts, which some public health experts worry could slow the response.

How to protect yourself

You can’t wash Cyclospora off with a quick rinse, and it doesn’t always come off produce reliably. What does kill it is heat. Cooking produce to 158 degrees Fahrenheit or higher wipes the parasite out.

If you do come down with prolonged watery diarrhea, the treatment is a specific antibiotic, trimethoprim-sulfamethoxazole, sold as Bactrim or Septra, usually taken for about 10 days. It’s worth seeing a doctor, since cyclosporiasis won’t respond to the usual anti-diarrhea approaches and can keep coming back in waves.

For now, the smart move is basic caution with fresh produce and paying attention to how you feel a week or so after eating.

If you keep an eye on the health stories making the rounds, the new world screwworm warning is another one worth knowing about. For more on the alerts affecting daily life, follow our Trending section.

Until investigators pin down the source, the parasite’s origin is the biggest open question, and the case count keeps climbing.