In parts of the country, including southeast Michigan and northern Ohio, clinicians are tracking scores of cases of sudden, explosive diarrhea and gastrointestinal illness caused by the parasite Cyclospora cayetanensi.
Michigan now has 1,251 cases of cyclosporiasis, according to state officials today, more than doubling the case count reported over the July 4 weekend. Typically, Michigan reports around 50 cases per year, but during the last week of June state officials first noted an outbreak of 170 cases that has since skyrocketed.
Of the 1,251 patients, 44 have been hospitalized, according to the case count.
In Ohio counties that border southeast Michigan, officials are tracking more than 500 cases, including 306 in Lucas County, the Associated Press reports. In an update yesterday, however, the Ohio Department of Health (ODH) confirmed only 177 cases statewide as of July 2, with 28 people hospitalized. Most cases have occurred since June 20, the ODH said.
Officials tell restaurants to wash produce carefully
No source has been identified in the outbreaks, but the Michigan Department of Health & Human Services (MDHHS) is now recommending enhanced washing procedures for “restaurants, commercial kitchens, and other entities preparing or serving raw produce in Southeast Michigan.”
The recommendations include careful washing of lettuce, herbs, green onions, raspberries, and snow peas, all foods associated with past Cyclospora outbreaks.
“Cyclosporiasis is not usually life-threatening, but dehydration from frequent bouts of diarrhea can cause severe illness, particularly among younger or older people and those who have weakened immune systems,” the MDHHS said. “The time between being exposed and becoming sick is usually about one week but can range from two days to two weeks or more. Untreated, the illness may last from a few days to more than a month. Symptoms may go away and then return.”
Surveillance has been optional for 1 year
While it may seem as though Michigan is the epicenter of US Cyclospora activity, true case counts are unknown. As of July 1, 2025, FoodNet, the main foodborne illness surveillance arm of the Centers for Disease Control and Prevention (CDC), made tracking Cyclospora optional.
Currently state health departments are required to survey for just two pathogens: Salmonella and Shiga toxin–producing Escherichia coli (STEC), which cause the largest foodborne illness outbreaks in the United States. Some states, including Michigan, have maintained Cyclospora surveillance.
And the CDC is not keeping up with national data on recent outbreaks. The agency last posted an update on activity on July 1, which lists only 145 cases nationwide through June 16, with 20 hospitalizations.
