A Diarrhea-Causing Parasite Is Surging Across the U.S. — and the CDC's Early-Warning System Isn't There to Catch It

A parasitic stomach illness that causes "explosive" watery diarrhea is spreading through dozens of U.S. states this summer — a year after the Trump administration quietly stripped away the federal surveillance system built to catch outbreaks like it before they grow. In July 2025, the administration scaled back FoodNet, the CDC's foodborne illness tracking program, to two mandatory pathogens — salmonella and E. coli — making surveillance of cyclospora and five other pathogens optional for participating states. One year later, cyclospora is the pathogen driving the largest cyclosporiasis outbreak in years, and the country is having to track it half-blind.

As of July 13, more than 4,000 cases of cyclosporiasis have been reported nationwide, according to a state-by-state tally compiled by NBC News, while the CDC's own count stood at 843 confirmed cases across 31 states as of July 9. Michigan has been hit hardest, with 2,640 cases and 44 hospitalizations reported by the state health department — roughly 50 times the state's typical annual total. Ohio, Illinois, New York and North Carolina have also reported sharp increases.

Health officials still don't know what's causing it. Investigators have not identified a common food source, and the CDC has said it has no evidence connecting the cases into a single, multistate outbreak — a determination made harder by gaps in the very system meant to make it.

That system, known as FoodNet, is a three-decade-old partnership between the CDC, USDA and state health departments that historically monitored eight major foodborne pathogens, including cyclospora, campylobacter, listeria, shigella, vibrio and yersinia. The CDC also dissolved its Division of Parasitic Diseases and Malaria that same year, reassigning remaining staff elsewhere in the agency — further thinning the ranks of specialists equipped to trace a parasite outbreak like this one.

Internal CDC talking points obtained by NBC News attributed the cutback to funding, stating that budget had "not kept pace with the resources required" to maintain surveillance of all eight pathogens. A CDC spokesperson at the time suggested state health departments could fill the gap. Colorado, one of the states that lost FoodNet funding for cyclospora surveillance, cut back its own monitoring in response — and is now experiencing an outbreak of its own.

Public health researchers say the timing is not a coincidence. Craig Hedberg, a professor in the Division of Environmental Health Sciences at the University of Minnesota, rejected the CDC's characterization of the surveillance as duplicative, arguing the cuts "normalize the idea that foodborne disease surveillance is expensive and unimportant" when it is in fact "the foundation of our food safety system."

The consequences are visible in how the outbreak has unfolded. For weeks, the CDC's public case count lagged far behind what states were reporting on their own — the federal dashboard showed just 145 cases nationwide through mid-June even as Michigan's count alone had already climbed past 1,200. Tracing the source has also proven difficult: because symptoms of cyclosporiasis can take one to two weeks to appear after exposure, investigators depend on patients accurately recalling what they ate — a task complicated when there are fewer federal epidemiologists coordinating that detective work across state lines.

For now, health officials are urging the same precautions that predate the cuts: wash produce thoroughly, cook leafy greens when possible, and avoid pre-washed bagged salad mixes tied to prior outbreaks. But those precautions can only do so much when the system meant to catch an outbreak like this early — and shut it down before it spread to tens of thousands of Americans — is the same one the administration dismantled a year before it happened.