Michigan officials link lettuce to Cyclospora outbreak of 2,640 cases

Michigan health officials have identified lettuce and salad greens as a potential source of a widespread Cyclospora outbreak that has infected at least 2,640 people since June 22, according to multiple reports. The state’s Department of Health and Human Services (MDHHS) emphasized that while no specific produce, grower, or supplier has been confirmed as the source, early investigations point to leafy greens as a common factor among cases. The parasite, which causes cyclosporiasis, leads to symptoms such as watery diarrhea, nausea, stomach cramps, and fatigue, with some cases lasting weeks if untreated.

Dr. Natasha Bagdasarian, Michigan’s chief medical executive, stated in a July 13 statement that investigators are focusing on fresh produce, particularly lettuce, but cautioned that other food items cannot be ruled out. “We will continue to provide updates as we learn more,” she said. The MDHHS has interviewed over 1,000 individuals affected by the outbreak, collaborating with federal agencies to trace the source. However, the complexity of food distribution networks and the parasite’s long incubation period—ranging from two days to two weeks—have slowed progress, according to officials.

The outbreak has spread across 21 Michigan counties, with the highest case numbers in southeastern regions. While the state’s health department has issued recommendations to wash leafy greens thoroughly and avoid pre-washed bagged products, the CDC reported 843 confirmed cases nationwide as of July 10, with over 1,500 suspected cases across 31 states. The discrepancy between state and federal data highlights challenges in tracking outbreaks, as the CDC noted delays in processing and reporting case information.

Investigations face additional hurdles, including the parasite’s resilience to chlorine and its ability to persist in environmental samples. Some experts, such as former FDA officials, have raised concerns that the focus on food may overlook waterborne transmission. Cyclospora can contaminate irrigation systems, soil, and floodwaters, particularly after heavy rainfall, which has been reported in Michigan and Ohio. “The role of water in transmission is probably underestimated,” said Frank Yiannas, a former FDA deputy commissioner. “We don’t have enough data on water sources, and that’s a gap in our surveillance.”

Funding cuts to public health infrastructure have further complicated efforts. The Trump administration’s 2025 reductions to FoodNet, a federal surveillance program, narrowed the scope of pathogens monitored, including Cyclospora. Barbara Kowalcyk, a public health researcher, argued that these cuts have limited the ability to track outbreaks effectively. “It’s like putting a puzzle together with pieces missing,” she said. Michigan’s public health labs, for example, lost $5.5 million in grants, according to local reports, which experts say has strained investigative capacity during the outbreak.

The CDC has maintained that Cyclospora remains a nationally reportable disease, with state health departments forwarding case data through the National Notifiable Disease Surveillance System. However, delays in reporting and the lack of a centralized, real-time tracking system have frustrated both officials and the public. “National counts often lag behind state reports,” said Craig Hedberg, a University of Minnesota environmental health professor. “This is not optimal for timely updates.”

Despite the challenges, Michigan officials have urged residents to take precautions, especially those at higher risk of dehydration, such as immunocompromised individuals and young children. The state has also advised healthcare providers to test for Cyclospora in patients with prolonged diarrhea. Treatment typically involves antibiotics, though untreated infections can persist for weeks. The outbreak has reignited debates over the adequacy of food safety regulations and the need for expanded surveillance of waterborne pathogens.

As investigations continue, the focus remains on identifying the exact source of contamination. While lettuce and salad greens are the leading suspects, officials caution that the outbreak’s complexity may involve multiple factors. “There is clearly a linked outbreak happening right now,” said Dr. Bagdasarian. “We’re working as quickly as possible to protect the public.”