Diarrhoea Outbreak From Cyclospora Parasite Surges A Year After CDC Downgraded Parasite Tracking

A parasite that causes explosive, watery diarrhoea has sickened thousands of Americans this summer, as public health officials investigate one of the country's largest cyclosporiasis outbreaks in recent years, striking just a year after the federal government stopped requiring health departments to track it.

Cyclosporiasis, an intestinal illness spread through contaminated fresh produce and water, has driven case counts to extraordinary highs across at least 25 states, with Michigan alone recording more than 1,500 infections against a typical annual tally of around 40 to 50. The surge has arrived while the Centres for Disease Control and Prevention (CDC) no longer requires its flagship foodborne surveillance network to monitor the parasite, a change that took effect on 1 July 2025.

Public health experts warn that the weakened national picture is making it harder to pinpoint the source of the contamination, though no investigator has yet linked the change in tracking to the scale of the outbreak.

Michigan Records Case Counts Roughly 25 Times Its Annual Average

The Michigan Department of Health and Human Services has reported 1,562 cyclosporiasis cases since late June, a figure a department spokesperson told NBC's TODAY is nearly 25 times higher than the state's usual 40 to 50 cases a year. Most infections cluster in eight south-eastern counties, including Wayne, Washtenaw, and Monroe.

Neighbouring Ohio has tracked hundreds more cases across counties bordering Michigan. The illness produces frequent, sometimes explosive diarrhoea, cramping, nausea and fatigue, with symptoms typically appearing about a week after exposure and, if untreated, lasting from a few days to more than a month.

No source of the contamination has been identified. The Michigan health department has urged restaurants and commercial kitchens in the affected region to wash lettuce, herbs, green onions, raspberries, and snow peas with extra care, all foods tied to past outbreaks.

CDC's National Surveillance Lags Far Behind State Numbers

The gap between what states are seeing and what the federal government reports has grown stark. The CDC's national surveillance page now lists 843 confirmed domestic cases since 1 May 2026, with more than 1,500 further cases awaiting confirmation, and acknowledges that true totals are almost certainly higher because many people recover without being tested.

For much of the outbreak, the agency's public tally moved slowly. As recently as early July, the CDC page showed only 145 cases nationwide through 16 June, even as Michigan's count alone climbed past 1,200. The CDC itself cautions that it assumes a six-week lag between when someone falls ill and when a case is reported to the agency.

The agency has said the rising counts do not yet appear to represent a single, linked multistate outbreak, and investigations with the Food and Drug Administration into several clusters remain ongoing.

The people falling ill span a wide range. Among the 843 domestically acquired cases, patients ranged in age from 5 to 88, with a median age of 44, and 59% were female, according to the CDC. Eighty-six of them were admitted to the hospital, though no deaths have been recorded. A separate group of 343 travellers picked up the parasite abroad, 18 of whom were hospitalised.

FoodNet Made Parasite Reporting Optional From July 2025

The surveillance change at the centre of the story concerns FoodNet, the Foodborne Diseases Active Surveillance Network run jointly by the CDC, the FDA, the US Department of Agriculture, and ten state health departments since 1995. From 1 July 2025, FoodNet reduced its required surveillance to just two pathogens, Salmonella and Shiga toxin-producing E. coli, making reporting of Cyclospora, Listeria, Campylobacter, Shigella, Vibrio and Yersinia optional.

The move was first reported by NBC News, which cited CDC talking points pointing to reduced federal funding. In a statement to the Centre for Infectious Disease Research and Policy, a Department of Health and Human Services spokesperson said FoodNet was concentrating on Salmonella and E. coli because they rank among the top five causes of foodborne illness, hospitalisation and death, and argued that other CDC systems still track the remaining pathogens.

Independent experts have questioned that reasoning. Craig Hedberg, a University of Minnesota food safety specialist, warned that cutting FoodNet 'normalises the idea that foodborne disease surveillance is expensive and unimportant', calling the network 'the foundation of our food safety system'. Public health consultant Gail Hansen said reduced surveillance could hamper efforts to detect and warn the public about outbreaks before they spread, since individual states cannot coordinate data across borders as FoodNet did.

FoodNet was built in the wake of the deadly 1992-93 E. coli outbreak linked to Jack-in-the-Box hamburgers, and Cyclospora was added to its watch list in 1997. Its ten participating jurisdictions include Colorado, Connecticut, Georgia, Maryland, Minnesota, New Mexico, Oregon, Tennessee, and parts of California and New York. Several states have opted to keep monitoring all eight pathogens regardless of the federal downgrade, with Minnesota and Maryland confirming they will continue tracking, while Colorado officials said they may have to scale back.

The parasite is surging through American kitchens at the precise moment the country chose to watch for it less closely.