Key takeaway:
- Michigan and Ohio have reported more than 3,000 cases tied to a cyclospora parasite outbreak, and investigators say lettuce or salad greens may be possible sources, though no specific product or supplier has been confirmed.
- The outbreak is difficult to trace because symptoms appear weeks after exposure, making patient recall and source identification challenging.
- Health officials advise people to wash produce thoroughly, use whole heads of lettuce when possible, and note that no nationwide food recall has been issued.
Michigan health officials are investigating whether lettuce or salad greens are connected to a cyclospora parasite outbreak that has sickened more than 3,000 people in Michigan and Ohio, though no specific product or supplier has yet been identified.
Michigan reported 2,640 confirmed cases as of Monday morning, including 44 hospitalizations, while Ohio has reported 361 cases since June 1, with at least 46 hospitalizations. Health officials said the investigation remains active and other foods have not been ruled out.
Michigan officials investigate possible source
State investigators said early interviews point to lettuce as a commonly reported food among patients. Still, evidence is not yet strong enough to identify a specific source or issue a recall.
“Early information has shown lettuce as a common product that regularly comes up during the investigation,” Michigan Chief Medical Executive Dr. Natasha Bagdasarian said in a statement Monday.
Bagdasarian said identifying the source will take time because investigators must interview thousands of patients about meals they consumed weeks before becoming sick. More than 1,000 interviews have already been completed.
Officials also review grocery loyalty card records and restaurant receipts to trace food purchases. Some restaurants have voluntarily removed certain fresh ingredients from their menus while the investigation continues, but Bagdasarian said there is no nationwide recall of any food linked to the outbreak.
Michigan health officials advise consumers to wash produce thoroughly, buy whole heads of lettuce instead of pre-washed varieties when possible, and remove outer leaves and wash inner leaves before eating.
Surveillance challenges slow outbreak response
The U.S. Centers for Disease Control and Prevention said 31 states had reported cyclospora cases as of July 10, although it remains unclear whether all are connected to the current outbreak. The agency reported 843 confirmed cases nationwide since May 1, noting that state totals are often higher while cases undergo additional analysis.
Public health experts said tracking a cyclospora parasite outbreak is more difficult than tracing bacteria such as salmonella or E. coli, because the parasite cannot be matched to contaminated food using the same rapid genetic techniques.
“I don’t think it’s in our country’s interest to cut these programs back,” former CDC Director Dr. Robert Redfield told CNN. “Surveillance is sort of the key to early identification.”
The CDC reduced FoodNet surveillance in 2025, limiting routine monitoring to Salmonella and a dangerous strain of E. coli. Cyclospora remains a nationally reportable disease through other surveillance systems, according to the U.S. Department of Health and Human Services.
“FDA and CDC are actively engaged with state partners to identify the source of the growing number of illnesses,” HHS spokesperson Emily Hilliard said in a statement.
Health officials urge produce safety measures
Cyclospora infections usually spread through contaminated fresh produce or water rather than direct person-to-person contact. Michigan officials said there is currently no evidence linking recreational water to the cyclospora parasite outbreak.
Symptoms include prolonged watery diarrhea, stomach cramps, and bloating, which can last for weeks and sometimes require hospitalization because of dehydration. The infection is typically treated with a seven- to 10-day course of antibiotics.
Health officials said confirmed case counts likely underestimate the true number of illnesses because patients may delay seeking medical care, and laboratory testing can require multiple stool samples before the parasite is detected.
Michigan officials said the investigation will continue as they work to identify a common source and prevent additional illnesses.
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