Cyclosporiasis Outbreak 2026: What to Know About the Suspected Lettuce Link

Health officials in Michigan said Monday that lettuce or salad greens are the leading suspected source of a Cyclosporiasis outbreak that has sickened more than 2,640 people in the state since late June. Ohio has reported an additional 361 cases tied to the same regional surge, and cases are climbing in multiple other states.

The finding marks the clearest lead yet in an investigation that has challenged public health officials for weeks. It matters because cyclosporiasis, a parasitic intestinal illness, is unusually hard to trace, and this outbreak is already one of the largest in the country in years, with Michigan alone reporting more than 50 times its typical annual case count.

The Michigan Department of Health and Human Services said current test results point to lettuce or salad greens, though it cautioned that “other food items cannot be completely ruled out.” No specific type of product, grower or supplier has been identified. Dr. Natasha Bagdasarian, the department’s chief medical executive, said early data has “shown lettuce as a common product” recurring throughout the investigation.

As of Monday, Michigan had recorded 44 hospitalizations linked to the outbreak, while Ohio had confirmed at least 46. Health officials in Michigan said they have completed more than 1,000 patient interviews as part of the effort to trace a common source, working alongside local, state and federal partners.

Cyclosporiasis is a microscopic parasite that causes watery diarrhea, nausea and stomach cramps. It spreads when people consume food or water contaminated with the parasite’s oocysts, most often through fresh produce exposed to contaminated irrigation water. Past U.S. and Canadian outbreaks have been linked to bagged salad mixes, cilantro, basil, raspberries, snow peas and green onions.

Tracing the source has been complicated by the parasite’s biology and by cuts to federal surveillance. Unlike bacteria such as E. coli or salmonella, cyclospora cannot easily be gene-matched between patient samples and contaminated food, so investigators must rely largely on interviews about meals eaten weeks earlier. Symptoms can take up to two weeks to appear, further widening the window investigators must examine. Separately, a federal foodborne-illness surveillance network that once tracked eight pathogens, including cyclospora, was scaled back last year and now monitors only two.

Nationally, the CDC has said it has identified elevated case counts in numerous states this year compared with the same period in 2025, when the country recorded roughly 2,700 cases for the full year. As of its most recent update, the agency said it has not found evidence connecting all of the reported cases to a single, multistate outbreak.

The outbreak underscores how difficult it has become to track contaminated produce nationally, particularly as surveillance resources have shrunk. A growing case count with no confirmed source leaves consumers with limited guidance on which products to avoid, even as illnesses continue to accumulate across state lines.

Michigan and Ohio health officials said their investigations remain active, and results are expected to take additional time given the outbreak’s scale. Officials said they are awaiting more states to report data to the CDC so investigators can determine whether the various regional case clusters are connected. Until a specific product is identified, health authorities are advising consumers to buy whole heads of lettuce rather than bagged or pre-washed greens, discard the outer two to three leaves, wash remaining leaves thoroughly under running water, and cook produce when possible. Anyone with persistent watery diarrhea is advised to see a health care provider and specifically request cyclospora testing, since routine stool tests often miss the parasite. The illness is typically treated with antibiotics along with fluids to prevent dehydration.