A surge in Cyclospora infections has affected at least 31 US states, with over 3,000 cases documented as of July 10, 2026. Michigan is the hardest-hit state, reporting 1,562 cases and 44 hospitalizations, according to state figures. Ohio is also experiencing a significant outbreak, with more than 500 cases in the northwest region alone.
This represents the largest Cyclospora outbreak in Michigan's history and one of the most significant nationwide in recent years. No deaths have been reported, and the source of contamination remains unknown. Investigations are ongoing in 28 other states, including Ohio, where residents near the Michigan border are falling ill.
Outbreak Timeline and Spread
Michigan officials first announced the outbreak last week when over 170 cases were confirmed, all clustered in the southeastern region since June 22. The state typically records only about 50 cases annually. By July 8, the number had surged to 992 cases with roughly 40 hospitalizations. In Lucas County, Ohio, 306 cases were reported by the same date.
The U.S. Centers for Disease Control and Prevention (CDC) is tracking the outbreak. Cyclospora outbreaks are notoriously difficult to investigate due to challenges in identifying contaminated food sources.
What Is Cyclospora?
Cyclospora is a microscopic, spherical parasite that causes cyclosporiasis, an illness characterized by watery diarrhea with frequent and sometimes explosive bowel movements. The disease is rarely fatal and is typically treated with antibiotics. Infections often peak in late spring and summer, as the parasite thrives in heat and spreads via fecal matter.
People usually contract the infection by consuming fruits or vegetables exposed to irrigation water contaminated with feces. It is less common than other foodborne illnesses like salmonella and E. coli.
Rising Cases and Expert Insights
While only a few Cyclospora outbreaks were recorded annually in the past, cases began rising about ten years ago, with a dramatic increase in 2018 and 2019. Specialists attribute the uptick to climate change and improved detection methods. The current number of cases is four times higher than at the same time last year, according to CDC national data, though state-level reports may lag.
Dianna Blau, acting chief of the CDC's parasitic diseases branch, stated there is no evidence the parasite has become more infectious. However, thousands of infections are reported each year, and it remains unclear how significant this year's figures will be. Michigan's proactive investigation and reporting may partly explain why the state appears disproportionately affected, according to state epidemiologist Dr. Natasha Bagdasarian.
Prevention and Advice
Officials advise anyone with diarrhea lasting more than a few days to seek medical advice and consider Cyclospora infection. To prevent infection, avoid potentially contaminated food or water. Wash fresh fruits and vegetables thoroughly before eating, though Cyclospora can cling to certain foods, so washing alone may not eliminate the risk.
Michigan authorities recommend purchasing whole lettuce heads instead of pre-washed packaged lettuce, discarding the outer two to three leaves, and washing the remaining leaves under running water. Cooking vegetables whenever possible is also advised.
