Health officials are investigating whether lettuce or salad greens may be linked to a growing Cyclospora outbreak, but no specific food item, supplier or grower has been identified as the source.
A Cyclospora outbreak that has sickened more than 3,000 people in Michigan and Ohio is being investigated for a possible link to lettuce and other salad greens, health officials said.
Michigan officials said early findings from their investigation showed lettuce was a common product reported by people who developed infections. However, authorities stressed that the investigation is still ongoing and other foods cannot be ruled out.
“Early information has shown lettuce as a common product that regularly comes up during the investigation,” Dr. Natasha Bagdasarian, Michigan’s chief medical executive, said in a statement.
Cyclospora cases rise across Michigan and Ohio
According to CNN, Michigan has reported 2,640 Cyclospora cases as of Monday morning, including 44 hospitalizations. Ohio has reported 361 cases since June 1, bringing the total number of reported illnesses in the two states above 3,000.
At least 46 people have been hospitalized across both states.
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The US Centers for Disease Control and Prevention (CDC) said 31 states had reported Cyclospora cases as of July 10, although it remains unclear whether all reported illnesses are connected to the same outbreak.
The CDC said multiple states have recorded an increase in cases over the past two weeks compared with the same period in 2025. The agency’s national count stood at 843 confirmed cases since May 1 while state-reported cases undergo further analysis.
Why is the Cyclospora outbreak difficult to trace?
Finding the source of Cyclospora outbreaks can be more complicated than tracking other foodborne illnesses such as E. coli or salmonella.
Those bacteria can often be linked through genetic testing, where scientists compare DNA patterns from sick patients with samples collected from contaminated food or water. But the same method is not as effective for Cyclospora.
Jennifer McEntire, a microbiologist and founder of Food Safety Strategies, explained that tracking Cyclospora is significantly more complex.
“For the bacterial pathogens, the technology is quite mature, and the organisms are really very, very simple. It’s like reading a children’s book versus reading ‘War and Peace’, cyclospora being the ‘War and Peace,’” McEntire said.
She added that while both involve genetic information, Cyclospora is much harder to analyze and trace.
Cases may be higher than official numbers
Health experts believe Cyclospora infections may be undercounted because many people with symptoms may not seek medical care or may try to recover at home.
The parasite usually spreads when people consume contaminated food or water. Symptoms can include persistent watery diarrhea, stomach cramps and bloating, and severe cases can result in dehydration and hospitalization.
Diagnosing the infection can also be challenging because Cyclospora may not always be detected in a single stool sample. Patients may require additional testing, and the parasite is not included in every standard gastrointestinal illness test.
Michigan officials said identifying the source will take time because investigators must review the eating histories of thousands of people and account for the complexity of food distribution networks.
“It actually requires us looking at every item they’ve ordered in a restaurant, what was in those menu items, and it requires pulling their shopper cards,” Bagdasarian said.
