Parasitic Cyclosporiasis Outbreak Spreads Across Michigan and US, With Over 300 Cases Reported

A major outbreak of cyclosporiasis is spreading across Michigan, with over 300 confirmed cases reported by July 2, 2026, far exceeding the state's typical annual average of 50 cases. The infection, caused by the microscopic parasite Cyclospora cayetanensis, triggers severe gastrointestinal symptoms like explosive diarrhea. While health officials in Michigan and neighboring Ohio investigate local clusters, the CDC has not yet identified a single, unified multistate source linking the cases.

Michigan cyclosporiasis outbreak

• ▪The Michigan Department of Health and Human Services is tracking a large and growing outbreak of cyclosporiasis, with more than 300 confirmed cases in Michigan as of July 2, 2026
• ▪Michigan typically records only about 50 cases of cyclosporiasis per year

Cyclospora parasite transmission

• ▪Cyclosporiasis is caused by a microscopic, unicellular parasite called Cyclospora cayetanensis, which is common in tropical and subtropical regions
• ▪The Cyclospora parasite is transmitted through food or water contaminated with infected feces and is not known to spread directly from person to person

Outbreak investigation efforts

• ▪The Centers for Disease Control and Prevention stated on July 1, 2026, that it has no evidence of a single, multistate Cyclospora outbreak linking the current cases
• ▪The Toledo-Lucas County Health Department in Ohio is investigating 65 cases of cyclosporiasis identified between June 25 and July 1, 2026

Cyclosporiasis symptoms

• ▪Without treatment, cyclosporiasis symptoms can last from a few days to a month or longer, and the infection is typically treated with the antibiotic trimethoprim-sulfamethoxazole
• ▪The main symptom of cyclosporiasis is watery, explosive diarrhea, which can be accompanied by abdominal cramps, bloating, loss of appetite, weight loss, and nausea

Food safety prevention measures

• ▪The Michigan Department of Agriculture and Rural Development recommends washing all fruits and vegetables thoroughly under running water and refrigerating cut, peeled, or cooked produce within two hours
• ▪Health officials advise scrubbing firm produce like melons and cucumbers with a clean brush and cutting away damaged or bruised areas to prevent infection

Historical produce-linked outbreaks

• ▪Previous U.S. cyclosporiasis outbreaks have been linked to imported fresh produce, including basil, cilantro, mesclun lettuce, raspberries, and snow peas
• ▪In 2018, McDonald's restaurants in Illinois and Iowa were identified as the source of a Cyclospora outbreak linked to salads that sickened 61 people across seven states