U.S. federal and state health officials are investigating a large cyclosporiasis outbreak linked to contaminated iceberg lettuce, with more than 12,000 cases reported across nine states so far this summer. On July 24, 2026, authorities confirmed that Illinois, Kansas, Oklahoma, and Pennsylvania had joined Indiana, Kentucky, Michigan, Ohio, and West Virginia in the active outbreak cluster. Michigan currently accounts for the majority of confirmed infections. The illness is caused by Cyclospora cayetanensis, a microscopic parasite transmitted via fecally contaminated food or water, and is characterized by severe diarrhea and related gastrointestinal and systemic symptoms after a one- to two-week incubation period.

Prepared by Olivia Bennett and reviewed by editorial team.