Cyclospora outbreak tops 3,000 cases in Michigan, Ohio

An outbreak of diarrhoea linked to the parasite Cyclospora has surpassed 3,000 cases in Michigan and Ohio, with investigators increasingly focusing on lettuce and salad greens as a possible source of the infections.

Health officials in Michigan cautioned, however, that other foods remain under investigation and that no specific product, grower or supplier has yet been identified, Caliber.Az reports, citing CNN.

"Early information has shown lettuce as a common product that regularly comes up during the investigation," Michigan Chief Medical Executive Dr. Natasha Bagdasarian said in a statement.

Michigan had recorded 2,640 cases as of Monday morning, including 44 hospitalisations, while Ohio reported 361 infections since June 1. Combined, the outbreak has resulted in at least 46 hospital admissions.

The U.S. Centres for Disease Control and Prevention (CDC) said 31 states had reported cyclospora cases as of July 10, although it remains unclear whether all are connected to the same outbreak.

According to the agency, "multiple states" have seen an increase in infections over the past two weeks compared with the same period last year. The CDC's national count stood at 843 confirmed cases since May 1 as of Friday, a figure lower than state totals because additional laboratory analysis is still underway.

Tracing the origin of cyclospora outbreaks is often challenging. Patients may need to remember foods consumed several weeks earlier, while laboratory testing and genetic analysis can take considerable time.

Public health experts also point to recent reductions in disease surveillance resources as an additional challenge.

Following staff and funding cuts in 2025, the CDC scaled back its FoodNet surveillance system, a partnership involving the CDC, the U.S. Department of Agriculture, the Food and Drug Administration and health departments in 10 states.

FoodNet previously monitored eight major foodborne pathogens, including Cyclospora, by proactively collecting laboratory results rather than waiting for cases to be reported. Since July 2025, however, the system has focused primarily on salmonella and a particularly dangerous strain of E. coli, with monitoring of other pathogens becoming optional.

Cyclospora infections remain nationally reportable diseases, meaning confirmed cases continue to be submitted to state health departments and eventually to the CDC.

Nevertheless, experts warn that the reduction in surveillance capacity has weakened the country's ability to quickly detect and track outbreaks involving the parasite.

By Bakhtiyar Abbasov