Cyclospora Parasite Sickens Thousands Across 34 States as CDC Flags Surveillance Gaps

A parasitic intestinal illness that most clinicians see only a few times a year is spreading at a pace that's catching public health workers off guard. As of July 13, the CDC had confirmed 1,645 laboratory-verified cases of cyclosporiasis acquired inside the United States, with no international travel link, across 34 states. A further 5,100 cases were awaiting classification, according to a report reviewed by Infection Control Today. The case count represents more than a sixfold increase over the same period in 2025.

The outbreak has a clear epicenter. Investigators have identified a concentrated multistate cluster of more than 400 cases in Michigan, Ohio, West Virginia, and Kentucky, with symptom onset on or after June 22. Michigan's Department of Health and Human Services has logged more than 1,000 patient interviews in its own investigation, and early results from those interviews point to lettuce or salad greens as a probable exposure vehicle, though no specific product or supplier has been confirmed. The MDHHS published updated guidance on July 13 recommending that consumers skip pre-washed bagged salad mixes entirely, buy whole heads of lettuce instead, and discard the outer two to three layers of leaves before washing the rest under running water.

Why the caution about bagged greens in particular? The parasite, Cyclospora cayetanensis, is resistant to the kinds of chemical disinfection that processing plants typically use. As the MDHHS guidance notes, pre-washed labeling does not guarantee safety and rewashing bagged lettuce is unlikely to remove cyclospora. Cooking greens to at least 158 degrees Fahrenheit is the only reliable kill step.

This is also an outbreak that's genuinely harder to track than it used to be. As CNN reported in its July 13 coverage, the CDC's FoodNet surveillance program, which once proactively collected cyclospora data by contacting labs directly rather than waiting for reports, dropped the parasite from its active monitoring roster before July 1, 2025, following federal staff and funding cuts. The network now actively collects data on only two pathogens: salmonella and a dangerous strain of E. coli. Cyclosporiasis remains a nationally notifiable disease, meaning confirmed cases still flow to the CDC through other channels, but the streamlined surveillance means investigators are working with a slower and narrower picture.

That lag matters clinically. Cases are slow to be counted partly because patients have to recall meals they ate weeks earlier: the parasite can take up to two weeks to produce symptoms after exposure, and the infection causes watery diarrhea, cramping, and bloating that can persist for weeks. Dehydration is what lands patients in the hospital. Of the 1,645 confirmed cases with available clinical data, 141, or about 9 percent, required hospitalization. No deaths have been reported.

The diagnostic side presents its own problem. Cyclospora is routinely missed in standard ova and parasite lab panels unless a clinician specifically orders it. Infectious disease specialists and gastroenterologists seeing patients with prolonged watery diarrhea should order targeted cyclospora testing, not just a standard stool panel. Treatment, when the diagnosis is caught, is seven to ten days of sulfamethoxazole-trimethoprim, sold as Bactrim or Septra.

FDA and CDC are both actively engaged with state partners, an HHS spokesperson confirmed in a statement to CNN, adding that roughly $33 million in annual funding for state foodborne disease activities has remained stable. But as Stateline reported on July 14, states such as Michigan are effectively doing their own investigative work to compensate for reduced federal-level surveillance capacity.

The CDC expects case numbers to keep climbing. There's typically a six-week lag between illness onset and when cases show up in national counts, which means the July 13 figures almost certainly understate where the outbreak stands today.

Sources cited:
- Infection Control Today (https://www.infectioncontroltoday.com/view/cyclosporiasis-outbreak-2026-1-645-confirmed-cases-34-states-with-growing-cluster-michigan-ohio-west-virginia-kentucky)
- CNN (https://www.cnn.com/2026/07/13/health/cyclospora-parasite-diarrhea-outbreak-increase)
- Michigan MDHHS Cyclosporiasis Outbreak page (https://www.michigan.gov/mdhhs/keep-mi-healthy/infectious-diseases/cyclosporiasis-outbreak)
- Stateline (https://stateline.org/2026/07/14/salad-greens-scrutinized-as-cyclosporiasis-outbreak-spreads/)