Cyclospora outbreak spreads across 34 states, sickening thousands

Cyclosporiasis has now been reported in 34 states, turning a parasitic foodborne illness that can cause severe, sometimes explosive diarrhea into a national outbreak tied to the way produce moves through the U.S. food supply. Federal investigators are still looking at contaminated produce as the likely source, with shredded iceberg lettuce among the items under scrutiny.

The Centers for Disease Control and Prevention said in a July 14 outbreak update that the U.S. had more than 1,600 lab-confirmed cases and more than 140 hospitalizations. Earlier in the outbreak, the count stood at 145 cases between the start of May and mid-June, then rose to 843 confirmed domestic cases since May 1, with more than 1,500 additional illnesses still needing analysis. That gap shows how hard cyclospora can be to pin down: symptoms often take time to appear, testing is not always immediate, and the reporting system itself has become less complete.

That reporting problem matters. The CDC’s surveillance rules changed in 2025, making cyclosporiasis reporting optional, a shift that has left public health officials with a thinner national picture just as the outbreak expands. Some state and local compilations have put the total at at least 6,756 cases in 38 states, a figure that reflects how much larger the outbreak may be than the confirmed federal count.

The geographic spread has pointed investigators to a broad distribution network rather than a single neighborhood exposure. Michigan, Ohio, Kentucky and West Virginia have repeatedly appeared in the same Midwest cluster, and some reporting has identified Michigan as the largest cluster. The CDC’s July outbreak pages include both an investigation update and a locations map showing where patients became sick, underscoring how the illness has been traced through scattered states rather than one obvious venue.

Food safety officials have focused on produce that is eaten raw, especially lettuce. Shredded iceberg lettuce has been examined as a possible source, and later reporting pointed to iceberg lettuce sourced from central Mexico as a potential link. That fits the broader pattern of cyclosporiasis outbreaks, which often emerge when a contaminated crop enters a wide retail and restaurant network before anyone realizes people are getting sick.

Hospitals and local health departments are seeing the impact first. By the time cases are counted, many patients have already spent days with severe gastrointestinal illness, and the delay between infection, diagnosis and reporting gives the parasite room to travel.