More than 1,200 people in Michigan have been infected with Cyclospora cayetanensis, a microscopic parasite that causes explosive, watery diarrhea, according to the Michigan Department of Health and Human Services. The outbreak, which has also spread to Ohio and 15 other U.S. states, has prompted investigations by the U.S. Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA). The Public Health Agency of Canada (PHAC) stated it is not currently investigating any cyclosporiasis outbreaks in Canada, but cases typically rise in spring and summer due to imported fresh produce.
Where Is the Outbreak?
As of July 10, 2026, Michigan reported 1,251 cases, up from 992 the previous day and 572 on July 6. Historically, the state averages only 40 to 50 cases annually. In Ohio, the Department of Health confirmed 177 cases as of July 2, with 28 hospitalizations. The CDC reports hundreds of additional cases across Illinois, New York, Pennsylvania, Texas, Alabama, Kentucky, Tennessee, Virginia, and West Virginia, though data after June 16 is not yet available.
What Is Cyclosporiasis?
Cyclosporiasis is a foodborne gastrointestinal illness caused by the single-celled parasite Cyclospora cayetanensis. Symptoms include explosive watery diarrhea, stomach cramps, nausea, and fatigue, which can last several weeks. The parasite is rarely fatal but can cause severe discomfort. Infection occurs when people consume food or water contaminated with human feces containing the parasite, often through fresh produce like berries, herbs, or lettuce grown in endemic regions.
What Is Causing the Outbreak?
Health officials are still trying to identify the source. The CDC stated, “CDC has no evidence of a single, multistate Cyclospora outbreak linking cases happening right now and being reported in the press.” Investigations are challenging because the parasite is not detected by routine stool tests, and patients often cannot recall what they ate due to the incubation period. Additionally, produce from multiple farms is often mixed during packaging, complicating traceback efforts. No cases have been linked to travel to endemic countries.
Canada’s Position
PHAC confirmed in an email to National Post that it is not currently investigating any Cyclospora outbreaks in Canada. However, Canadian cases typically increase in spring and summer as consumption of imported fresh fruits and vegetables rises. The agency noted that the parasite is not commonly found on domestic food or water. Canadians are advised to wash produce thoroughly and practice good hygiene to reduce risk.
