Michigan is experiencing an unusually large outbreak of cyclosporiasis, an intestinal illness caused by the microscopic parasite Cyclospora cayetanensis, with more than 700 cases and 36 hospitalisations reported since 22 June. The number of cases has risen sharply over a matter of days — from 170 on 30 June to 572 on 4 July and beyond 700 by 6 July — yet officials have not identified the source, making it a significant and still-developing public health concern.

The parasite spreads via faeces contaminating produce or water, and previous outbreaks have been tied to items such as bagged salads, cilantro, basil, raspberries, snow peas and green onions. The illness typically causes watery, sometimes explosive diarrhoea lasting a week or more, with dehydration the main risk. Michigan's health department is coordinating a large investigation with local authorities in the state's south-east, where most cases have occurred, and with the CDC. Notably, the CDC's public surveillance data has not been updated since 16 June and excludes Michigan's cases, with federal officials not responding to enquiries. The state's tally is far above its usual annual total of around 50 cases, though national figures so far appear consistent with recent years.