Michigan cyclosporiasis cases top 700 as officials search for food source

A surge of cyclosporiasis has sickened more than 700 people in Michigan in recent weeks, straining testing capacity and sending health officials into a race to identify a food source. The illness, caused by the microscopic parasite cyclospora, can bring prolonged diarrhea and dehydration if it is not treated, according to health officials and physicians cited by NBC News.

Dr. Natasha Bagdasarian, Michigan’s chief medical executive, told NBC News that the state recorded 708 cases in roughly 10 days. She called the rise “highly unusual,” saying Michigan usually sees about 40 to 50 cases in a year.

The Food and Drug Administration said an investigation is underway, NBC News reported. An FDA spokesperson said the agency and the Centers for Disease Control and Prevention are monitoring the outbreaks, but said the FDA was not yet ready to label the current numbers definitively unusual before the investigation is complete.

Most Michigan cases have been concentrated in the southeastern part of the state, according to NBC News. State health departments have also reported illnesses in Ohio, North Carolina, Illinois and New Jersey, among other states.

What cyclosporiasis is

Cyclosporiasis is a foodborne illness caused by cyclospora, according to the CDC. NBC News reported that fresh produce is often involved, and that earlier outbreaks have been linked to items including raspberries, bagged lettuce or salads, cilantro and basil.

The CDC says cases tend to rise in summer, especially from May 1 through Aug. 31. From the start of May through June 16, the CDC had received reports of 145 cases in 17 states, though NBC News reported those figures are likely an undercount.

A CDC spokesperson told NBC News the agency had no evidence of one single multistate cyclospora outbreak linking the cases now being reported. The CDC made cyclospora tracking optional in July 2025 as part of changes to its Foodborne Diseases Active Surveillance Network, NBC News reported at the time, a move food safety experts warned could make outbreaks harder to detect and address.

Symptoms and treatment

Doctors told NBC News that patients have been seeking care for severe watery diarrhea, abdominal cramps and other gastrointestinal symptoms. Reported symptoms can also include gas, nausea and loss of appetite.

Unlike norovirus, cyclosporiasis does not spread from person to person, NBC News reported. Without treatment, the illness can last for weeks, and doctors usually treat it with the antibiotic Bactrim.

Dr. Anurag Malani, vice chief of staff at Trinity Health Ann Arbor, told NBC News that some patients have been hospitalized, often because of dehydration. No deaths have been reported.

Dr. Brian Kaminski, vice president of medical affairs at ProMedica Health System, told NBC News that cases in southeast Michigan and northwest Ohio appear to be part of an “epidemic cluster.” ProMedica had counted 411 cases as of Monday, NBC News reported.

Search for the source

Bagdasarian told NBC News that investigators are asking patients about restaurants, grocery stores, recent orders and food purchases from the previous couple of weeks. She said staff have been working overtime and reviewing grocery lists as cases have climbed.

The investigation is complicated because symptoms can take one to two weeks to appear after someone eats contaminated food, according to NBC News. Testing delays are also growing in some areas: Kaminski said results that initially took about 24 hours were taking two to three days.

Health officials said washing produce can reduce risk but may not remove cyclospora entirely. Michigan officials are advising people to buy whole heads of lettuce, discard outer leaves and wash the rest, while doctors told NBC News that cooking food is the only certain way to kill the parasite.

This story draws on original reporting from NBC News.