Michigan parasite outbreak linked to lettuce as cases rise above 2,600

Michigan health officials have linked a fast-growing cyclosporiasis outbreak to lettuce or salad greens as the state’s case count surged to 2,640 and the search for the contaminated supply chain remained open. The outbreak has already sent 44 people to hospitals, and investigators have not identified a specific grower, supplier or produce type as the source.

The Michigan Department of Health and Human Services said the largest increase was concentrated in Southeast Michigan. Its early findings pointed to lettuce or salad greens, but the agency said other foods could not be ruled out, a reminder of how difficult it remains to trace contamination through produce that is often washed, bagged and repackaged before it reaches shoppers.

The scale in Michigan dwarfed the federal count. The Centers for Disease Control and Prevention said the 2026 cyclosporiasis season began on May 1 and that, as of July 9, it had received 843 confirmed domestic cases nationwide, with 86 hospitalizations and no deaths. The agency said it was aware of more than 1,500 additional cases that still needed analysis to confirm they were domestically acquired. CDC also said it would publish surveillance data more frequently than in previous seasons because the number of infections has risen sharply.

Cyclosporiasis is a parasitic illness that usually starts about a week after exposure, though symptoms can appear as soon as two days later or take two weeks or more. Untreated illness can last from a few days to more than a month, and symptoms may fade and return. Frequent diarrhea can cause severe dehydration, especially in young children, older adults and people with weakened immune systems.

Michigan officials have told restaurants, commercial kitchens and others serving raw produce in Southeast Michigan to buy whole heads of lettuce instead of prewashed bagged salads, remove the outer two to three leaves, wash inner leaves under running water and cook leafy greens when possible. The guidance reflects the challenge of policing leafy greens, which have been tied to past U.S. and Canada outbreaks linked to bagged salad mixes and kits, fresh cilantro, fresh basil, raspberries, snow peas and green onions.

The CDC said cyclosporiasis is a nationally notifiable disease and reportable in 47 states, the District of Columbia and New York City, but the latest Michigan outbreak shows how quickly a single produce-linked parasite can overwhelm tracing systems before the source is pinned down.