INDIANAPOLIS (WRTV) — Marion County is experiencing an unusual increase in confirmed case of the parasite Cyclospora, also known as "explosive diarrhea," during 2026, health officials reported Wednesday.
Typically, the county records three or four cases annually, but so far in 2026, 15 cases have been confirmed, said an email to News 8 from Curt Brantingham, media and public information coordinator for the Health & Hospital Corporation of Marion County and Marion County Public Health Department.
Cases of Cyclospora are reportable to the Marion County Public Health Department, which is monitoring the situation.
News 8 also emailed the Indiana Department of Health to learn of any breakouts in Indiana but did not immediately receive a reply.
The Associated Press reported Wednesday that 992 people in Michigan have been diagnosed with the parasitic infection that can cause weeks of watery diarrhea. It's the largest such outbreak in state history and one of the nation’s largest in years. No deaths have been reported and the source of the Cyclospora infections hasn't been identified. Meanwhile, investigations into similar illnesses have been going on in 28 other states, including in Ohio, where people just across the Michigan border are also becoming sick.
The Centers for Disease Control and Prevention says cyclosporiasis is an intestinal illness caused by the microscopic parasite Cyclospora cayetanensis. The exact way Cyclospora gets into food and water is not fully understood. The best way to prevent infection is to avoid consuming food or water that may be contaminated with feces.
Health officials advise residents to follow safe food handling practices to reduce their risk. Routine chemical disinfection or sanitization of food and water is unlikely to kill Cyclospora, particularly in tropical and subtropical regions where the parasite is more common.
Symptoms typically appear about one week after infection, though the onset can range from two days to two weeks. The CDC tracks confirmed cases that health officials at the local, state and federal levels report to the agency.
The CDC says it's received reports of 145 cases of cyclosporiasis acquired in the United States of people who became sick from May 1 through June 16.
The CDC has more information about "explosive diarrhea" on its website.
