A parasitic illness causing explosive, watery diarrhea has spread to 18 states, prompting federal health officials to investigate multiple potential clusters — even as the agency responsible for leading the response operates with a significantly diminished workforce following sweeping cuts by the Trump-Vance administration.
The U.S. Centers for Disease Control and Prevention reported 145 confirmed cases of cyclosporiasis acquired domestically between May 1 and June 16, 2026, spanning 17 states, with 20 hospitalizations and no deaths. Since then, a rapidly growing outbreak in Michigan has pushed the total case count above 400 across 18 states. The CDC is working alongside the Food and Drug Administration and local health officials to investigate several clusters and trace potential food sources.
A Familiar but Unusually Active Seasonal Parasite
Cyclosporiasis is caused by the microscopic parasite Cyclospora, which spreads through raw produce or water contaminated with human feces. Symptoms include watery diarrhea — sometimes described as explosive — along with cramping, nausea, fatigue, low-grade fever, and vomiting. The illness is seasonal in the United States, typically peaking between May and August, when consumption of fresh produce such as basil, cilantro, spinach, and berries is highest. These foods have been linked to past outbreaks.
What makes 2026 notable is the volume and geographic spread of cases. Michigan, normally recording around 50 cases annually, had reported more than 300 cases since June 22 alone. New York has logged 107 cases since May 1, and New York City saw case counts roughly double compared to the same period in 2025. New York, Texas, Illinois, and Michigan have been the hardest hit states, with additional cases reported in Alaska, Colorado, Connecticut, Florida, Georgia, Louisiana, Massachusetts, New Jersey, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, and Wisconsin.
The CDC has emphasized that there is currently no evidence linking all reported cases to a single, multistate outbreak. Investigators are instead pursuing multiple potential clusters with distinct food sources. The agency noted that the true number of cases is likely higher than reported, as some individuals recover without seeking medical care or being tested.
Outbreak Investigation Underway — With a Leaner Federal Workforce
The investigation is unfolding against the backdrop of deep and ongoing reductions to CDC’s capacity. Since early 2025, the Trump-Vance administration has cut more than 3,000 positions from the agency — roughly a quarter of its total workforce — through mass firings, early retirement incentives, and attrition. The CDC has also been without a permanent director for more than six months. Jay Bhattacharya, who simultaneously leads the National Institutes of Health, was recently named interim director.
Former CDC communications staffer Sarah Boim, who was terminated in the first wave of firings in February 2025, described the broader toll as generational. “The harm that’s going to come to people that don’t even know what CDC was protecting them from,” she said in a March 2026 report by WABE. A significant share of CDC funding flows directly to state and local health departments, and disruptions to those pass-through funds have further strained the public health infrastructure that underpins outbreak detection and response at the community level.
HHS has defended the reductions, with spokesperson Andrew Nixon stating that “HHS under the Biden administration became a bloated bureaucracy,” and that the department “continues to close wasteful and duplicative entities.”
What the Public and Providers Should Know
The CDC advises that individuals who experience symptoms consistent with cyclosporiasis should contact their healthcare provider. Antibiotic treatment is effective in more severe cases; most people with healthy immune systems recover on their own within days to weeks. Dehydration is a primary risk, and fluid intake is strongly recommended.
Cyclosporiasis is a nationally notifiable disease in 47 states and the District of Columbia. Healthcare providers who identify confirmed cases are asked to report them to their local health department to aid ongoing surveillance and investigation. The CDC also recommends thoroughly washing all fresh produce, hands, and kitchen surfaces before food preparation.
The illness is not typically transmitted person to person.
As federal investigators continue working to identify the sources driving this season’s elevated case counts, the outbreak arrives at a moment when the agency’s institutional capacity to respond quickly and comprehensively has been substantially reduced.
Sources and further reading:
CDC investigates parasite that’s caused cases of ‘explosive’ diarrhea in 18 US states – The Guardian
Cyclosporiasis Surveillance, July 1, 2026 – U.S. Centers for Disease Control and Prevention
Demoralized CDC Workforce Reels From Year of Firings, Funding Cuts, and a Shooting – Global Biodefense