The Centers for Disease Control and Prevention (CDC) has announced that outbreaks of cyclospora, a parasite causing watery and explosive diarrhea, are expected to continue across the United States through August. Federal health officials are actively investigating the food supply chain to identify the source of the contamination.
Current Case Numbers and Hospitalizations
The CDC has identified 1,645 laboratory-confirmed cases of cyclosporiasis, with 145 individuals requiring hospitalization. Additionally, there is a backlog of 5,100 cases that require further analysis, including patient interviews. Gwen Biggerstaff, deputy director of the CDC's Division of Foodborne, Waterborne, and Environmental Diseases, stated, "The true number of infections is almost certainly higher, because many people with mild illness recover. We're seeing an unusually high number of cyclosporiasis cases this summer."
Linked Outbreaks and Potential Source
Health officials have determined that outbreaks in Michigan, Ohio, West Virginia, and Kentucky are linked, though the exact source remains unidentified. On Monday, Michigan officials warned that lettuce is a "potential source" of the outbreak. According to the Washington Post, federal and state officials are investigating whether lettuce served at Taco Bell locations in Michigan may be connected to the outbreak. State officials have reported significantly higher numbers of sickened individuals than the CDC, likely due to reporting delays. Michigan officials reported over 2,800 cases in the state alone.
Characteristics of Cyclosporiasis
Cyclosporiasis is an intestinal infection caused by the single-cell protozoa Cyclospora cayetanensis. The parasite is typically transmitted through food or water contaminated with feces. Infections are most common during warm weather months, from May to August. The long incubation period, ranging from days to weeks, makes the parasite difficult to track. Diagnosis and reporting can take additional weeks, requiring patients to recall their food consumption from six to eight weeks prior.
Historical Context and Climate Change
Past outbreaks have been linked to bagged salads, herbs, raspberries, and lettuce. Experts believe that climate change may be increasing the prevalence of cyclosporiasis, as warmer temperatures allow the microbe to thrive. Federal and state officials advise thorough washing of fresh produce, with cooking being the most effective prevention method.
Challenges in Investigation and Response
Donald Prater, the FDA's acting deputy commissioner for food, noted, "Cyclospora remains a challenging agent. Our outbreak investigation team is hard at work to follow all the leads we have from CDC for all the various outbreak clusters we have." The Trump administration has faced criticism from public health experts for cutting $11.4 billion from state and local health departments and narrowing the scope of the CDC's FoodNet program, which surveils foodborne illness trends. Biggerstaff acknowledged that state budgets are tight but stated that the CDC is holding weekly calls with states and is "actively engaged."
Surveillance Gaps and Testing Recommendations
The CDC had previously warned that comprehensive efforts are needed to improve food safety, noting a 443% increase in cyclospora infections when comparing 2016–2018 to 2021. However, later communications suggested that the increase may reflect improved detection rather than a true rise in cases. Biggerstaff emphasized the importance of testing, stating, "The gap in surveillance I would like to focus on is people who would not seek care, and if they do seek care they don't get tested." She urged individuals concerned about cyclosporiasis to request a specific test, as the parasite may not be detected in standard stool panels.
