An outbreak of diarrhea caused by the cyclospora parasite has affected over 3,000 individuals in Michigan and Ohio, with lettuce suspected as a potential source.
Washington DC, United States Jul 14, 2026 ALN: An outbreak of diarrhea caused by the parasite cyclospora has surged to more than 3,000 confirmed cases in Michigan and Ohio, raising significant public health concerns. The ongoing investigation by health officials suggests that lettuce or salad greens might be the source of the outbreak, although no specific type, grower, or supplier has been definitively identified as responsible for the contamination.
Dr. Natasha Bagdasarian, Michigan’s chief medical executive, noted in a statement that preliminary information has highlighted lettuce as a common product involved in the investigation. However, she emphasized that other foods cannot be ruled out at this stage. The Michigan Department of Health and Human Services reported that as of Monday morning, the state had documented 2,640 cases of cyclosporiasis, including 44 hospitalizations. Meanwhile, Ohio has reported 361 cases since June 1, with at least 46 individuals requiring hospitalization due to severe symptoms.
As of July 10, a total of 31 states have reported cases to the US Centers for Disease Control and Prevention (CDC), although it remains unclear whether all these cases are linked to the same outbreak. The CDC indicated that its national count, which includes 843 confirmed cases since May 1, is lower than the states' reported counts, as cases are still undergoing further analysis. This discrepancy highlights the complexities involved in tracking foodborne illnesses and the challenges faced by health officials in identifying outbreaks promptly.
Investigators face numerous hurdles when attempting to pinpoint the source of the cyclospora outbreak. Cyclosporiasis cases are often slow to be counted, as they require patients to recall their dietary habits from weeks prior. This can complicate the investigation, especially when combined with genomic testing, which is a complicated process. Furthermore, public health systems that track foodborne illnesses have recently encountered sharp budget cuts, further hampering their ability to respond effectively to outbreaks.
In 2025, following significant reductions in staff and funding for public health agencies, the CDC scaled back its surveillance systems for foodborne illnesses. The FoodNet system, a collaborative effort between the CDC, the US Department of Agriculture, the US Food and Drug Administration, and ten state health departments, was designed to proactively identify cases of foodborne illness by directly contacting laboratories for test results. This system previously collected data on eight pathogens, including cyclospora, but now focuses only on two primary pathogens: salmonella and a particularly dangerous strain of E. coli. This reduction in scope means that tracking diseases like cyclosporiasis is less comprehensive than it once was.
Despite these challenges, cyclosporiasis remains a nationally notifiable disease, meaning that confirmed cases must be reported to state health departments and subsequently to the CDC. However, the cuts to funding and resources have left the surveillance system less robust than it was previously. Former CDC Director Dr. Robert Redfield expressed concern over these reductions, stating, "I don’t think it’s in our country’s interest to cut these programs back. Surveillance is sort of the key to early identification."
The US Department of Health and Human Services has acknowledged that cases of cyclosporiasis tend to rise during the summer months, and they are collaborating with federal and state partners to monitor case counts and cluster activity. Emily Hilliard, a spokesperson for the department, confirmed that the FDA and CDC are actively engaged with state partners to identify the source of the increasing number of illnesses. She also noted that the CDC continues to collect data on cyclospora through other surveillance systems, maintaining that funding for state foodborne disease activities has remained stable at approximately $33 million annually.
Cyclospora is a particularly challenging pathogen to trace compared to others, such as E. coli and salmonella. With bacterial pathogens, scientists can sequence their DNA to match a strain making people sick with a strain contaminating food or water. This gene matching is crucial for identifying outbreaks of foodborne illness. A national network of surveillance laboratories, known as PulseNet, continuously sequences the genes of bacteria that cause illness in order to compare the DNA fingerprints of cases in near real-time. When a match is found across multiple cases in different states, it signals the need to investigate a common source.
However, gene matching does not work as effectively for cyclospora. Jennifer McEntire, a microbiologist and founder of Food Safety Strategies, explained that the technology for tracking cyclospora is not as advanced as it is for bacterial pathogens. She likened the complexity of cyclospora to reading a challenging novel compared to a simple children's book, stating, "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.'" This complexity makes it significantly more difficult to trace the source of infections.
Cyclosporiasis does not typically spread directly from person to person; rather, individuals become ill by consuming contaminated food or water that has been tainted weeks earlier. Fresh produce and water from swimming pools are common sources of contamination. In an update, Michigan health officials stated that there is currently no evidence linking recreational water activities to the ongoing outbreak.
Symptoms of cyclosporiasis can include watery diarrhea, cramping, and bloating, which can persist for weeks. Dehydration resulting from these symptoms can lead to hospitalization. Treatment typically involves a course of antibiotics, specifically a combination of sulfamethoxazole and trimethoprim, commonly sold under the brand names Bactrim or Septra.
Health experts believe that the actual number of cyclosporiasis cases is likely an undercount. Many individuals experiencing symptoms of the infection may feel embarrassed to seek medical attention or may attempt to manage their symptoms at home without professional help. This reluctance can lead to a significant number of cases going unreported, complicating efforts to fully understand the scope of the outbreak and implement effective public health responses.
As the investigation continues, health officials remain vigilant in monitoring the situation, and the public is urged to exercise caution when consuming fresh produce, particularly lettuce and salad greens, until the source of the outbreak can be definitively identified and addressed.
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