A parasitic infection tied to contaminated lettuce is on track to make 2026 the worst year for cyclosporiasis in U.S. history, with confirmed cases already surpassing the entire total from 2025.
The CDC reported 4,173 confirmed cases between May 1 and July 20, dwarfing last year's total count. The outbreak now spans at least 41 states, though five states have been officially designated as outbreak zones where infection rates continue climbing.
Michigan leads by a wide margin, with between 900 and 2,100 lab-confirmed domestic cases. Using the midpoint of that range, the state is experiencing an estimated infection rate of nearly 15 cases per 100,000 people, far exceeding the other outbreak states. Ohio follows with 3.36 per 10,000 people, Indiana at 3.33, Kentucky at 2.61, and West Virginia at 1.16.
The illness, a diarrhea-inducing condition caused by the cyclospora parasite, has investigators focused on iceberg lettuce as the likely culprit. Health officials are treating the contamination as an ongoing food safety threat even as they work to contain spread.
The actual scope of the outbreak is almost certainly worse than confirmed numbers suggest. The CDC is aware of at least 7,400 additional cases, many from Michigan and Ohio, that have not yet received lab confirmation. Many infected people also never seek testing, meaning true case counts remain hidden.
While sporadic cyclosporiasis cases occur annually and a handful of cases in a given state would not trigger alarm, the concentration and velocity of this year's surge has become a legitimate public health concern. A lag between symptom onset and case reporting means the full picture of the outbreak may not be clear for several weeks.
Health officials are bracing for numbers to worsen before they improve. The outbreak's trajectory suggests case totals will likely continue climbing as investigations and mitigation efforts proceed.
Author James Rodriguez: "This is shaping up to be a serious wake-up call for the food safety system, especially if lettuce remains the vector."
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