Michigan tracks growing cyclosporiasis outbreak as cases top 170

Michigan health officials are investigating a large and growing cyclosporiasis outbreak after more than 170 cases were identified across seven counties in the nine days before June 30. The case count, which includes Monroe, Lenawee, Washtenaw, Wayne, Livingston, Shiawassee and Jackson counties, already far exceeds the roughly 50 cyclosporiasis cases Michigan typically identifies in a full year.

Monroe County had 67 cases as of June 29, with illnesses beginning in the previous week. The source has not yet been identified, even as the Michigan Department of Health and Human Services and the Michigan Department of Agriculture and Rural Development work with local health departments to trace where the parasite is coming from.

Cyclosporiasis is caused by Cyclospora cayetanensis, a parasite spread through food or water contaminated with feces. It is not known to spread from person to person. Symptoms usually start about a week after exposure, but they can appear as soon as two days later or as late as two weeks later, and untreated illness can last from a few days to a month or longer. Antibiotic treatment can significantly improve symptoms, making early medical care important for people with persistent diarrhea or other severe stomach illness.

Dr. Natasha Bagdasarian, Michigan’s chief medical executive, pointed to outbreaks across the United States and now in Michigan. Monroe County health officials have urged people to think back about where produce was purchased or whether they ate at restaurants about two weeks before they became sick.

The Centers for Disease Control and Prevention received reports of 145 domestically acquired cyclosporiasis cases from May 1 through June 16 across 17 states, with 20 hospitalizations and no deaths. There was no evidence of a single multistate outbreak linking all of those cases. Cyclosporiasis season runs from May 1 through Aug. 31.

Outbreaks have been tied to fresh fruits and vegetables, and chlorine and other common antimicrobial chemical treatments do not reliably kill Cyclospora cayetanensis. The parasite must remain in the environment for one to two weeks before it becomes infective to humans. Careful washing of produce and handwashing remain important protections while investigators work to find the source.