Cyclospora outbreak hits record 5,700 cases; Michigan suspects lettuce

A cyclosporiasis outbreak has surged to unprecedented levels across the United States, with confirmed and suspected cases totaling over 5,700 as of mid-July 2026—surpassing the previous U.S. record of approximately 4,700 cases set in 2019. The CDC has confirmed 1,645 domestic cases since May 1, with more than 5,100 additional cases under investigation across 34 states. Michigan has been the most severely affected, reporting more than 3,300 confirmed cases, a dramatic increase from the state's typical annual baseline of approximately 50 cases.

Based on interviews with over 1,000 infected patients in Michigan, state health officials have identified lettuce or salad greens as the leading suspect for the outbreak's source, though no definitive food source has been confirmed. Public health authorities have recommended that consumers purchase whole heads of lettuce, discard outer layers, and thoroughly wash remaining leaves. However, experts emphasize that the cyclospora parasite is notably resistant to washing and rinsing, and cooking produce to an internal temperature of at least 158 degrees Fahrenheit is required to eliminate the pathogen. At least four states—Michigan, Ohio, West Virginia, and Kentucky—appear epidemiologically linked, suggesting a possible common source for hundreds of cases across the region.

Cyclosporiasis, caused by a microscopic spherical parasite, typically produces watery diarrhea with frequent and sometimes explosive bowel movements, along with cramping, bloating, nausea, fatigue, and loss of appetite. Symptoms generally appear one to two weeks after infection, complicating outbreak investigations. Testing for cyclospora requires analyzing large quantities of potentially contaminated produce and multiple stool samples from patients, making the process far more complex than detecting other foodborne pathogens. No deaths have been reported, and the illness is typically treated with antibiotics, though symptoms can persist for more than a month without treatment.

Public health experts cite multiple obstacles to identifying the outbreak's origin. The one-to-two-week lag between exposure and symptom onset makes it difficult for patients to recall specific food sources. Additionally, the parasite is difficult to detect in environmental samples and food, and recent budget cuts to federal surveillance programs have reduced monitoring capacity. The Foodborne Diseases Active Surveillance Network (FoodNet) scaled back monitoring for all but two pathogens in the previous year, limiting the data typically available to support outbreak investigations. Some restaurant chains, including Taco Bell, have voluntarily removed certain produce items as a precautionary measure, though no official product recalls have been announced and public health officials have not confirmed any specific ingredient, supplier, or retailer as a source.

Experts attribute the rising trend in cyclosporiasis cases to improved detection methods and increased awareness among healthcare providers, who historically may have underreported cases. Some cases in certain states, such as Illinois, involved travel outside the United States, suggesting not all infections originated from a domestic source. As the investigation continues, health officials are conducting multi-state tracing efforts to identify the contamination point in the food supply chain.