JULY 9, 2026

Cyclospora outbreak in Michigan surpasses 1,000 cases, spreading into Ohio

An outbreak of cyclospora, a microscopic parasite that causes watery diarrhea, has grown to nearly 1,000 cases in Michigan and more than 500 in northwestern Ohio, making it the largest such outbreak in Michigan's history. No deaths have been reported, and health officials have not yet identified the source of the infections. Investigations into similar illnesses are ongoing in 28 other states.

Michigan officials first announced the outbreak last week, when more than 170 cases had been identified in the southeastern corner of the state since June 22. By Wednesday, the state reported 992 confirmed cases, including approximately 40 hospitalizations. Lucas County, Ohio, reported 306 cases as of Wednesday, and northwestern Ohio has seen more than 500 cases total. Michigan typically identifies only about 50 cyclospora cases per year.

Dr. Natasha Bagdasarian, Michigan's chief medical executive, told the Associated Press that "there is clearly a linked outbreak happening right now," while also noting that the state's aggressiveness in investigating and reporting cases may be "part of the reason why this looks like a Michigan problem." Dianna Blau, the CDC's acting parasitic diseases branch chief, said there is no evidence the parasite has evolved to become more infectious, and the situation is not considered a national health emergency.

Cyclospora is a heat-loving parasite that infects the bowels and spreads through feces. It commonly causes watery diarrhea "with frequent and sometimes explosive bowel movements," according to the CDC. The illness is not usually life threatening and is typically treated with antibiotics. Outbreaks tend to occur most often in late spring and summer. In the past, people have been infected by consuming fruits or vegetables exposed to feces-contaminated irrigation water.