Explosive Diarrhoea Outbreak Hits 34 States, Nearly 7,000 Cases as US Officials Struggle to Trace Source

Public health officials are struggling to pinpoint the origin of a fast-spreading parasitic outbreak that has sickened nearly 7,000 people across 34 states, with experts warning that the search for a source has been complicated by both the nature of the pathogen and cuts to federal health programs.

The outbreak involves cyclosporiasis, a parasitic infection typically spread through contaminated food or water that tends to surge during the summer months. Its main symptom is frequent, watery diarrhoea, and while the illness is rarely fatal, it can leave those infected severely uncomfortable for extended periods. According to the Centers for Disease Control and Prevention, Michigan has been hit hardest, with more than 3,300 reported cases, followed by New York state.

Health officials have advised the public to wash produce thoroughly, cook vegetables to kill off the parasite, and avoid certain fruits such as raspberries. Despite those precautions, the sources of contamination driving the outbreak remain unidentified.

A Notoriously Difficult Pathogen to Trace

Experts say cyclospora is inherently harder to track than many other foodborne pathogens. Steven Manderach, executive director of the Association of Food and Drug Officials, described the challenge in stark terms.

"This isn't like detecting a needle in a haystack. It's like detecting a microscopic portion of a needle in a haystack," Manderach said.

Part of the difficulty lies in the incubation period. Unlike many foodborne illnesses that produce symptoms within hours, cyclosporiasis can take one to two weeks to cause noticeable illness, according to Jodie Guest, senior vice chair of epidemiology at Emory University's Rollins School of Public Health.

"With most food-related illnesses, people tend to experience symptoms within a couple of hours, making it easier to find the food that caused them," Guest said.

Testing itself adds another layer of complexity. Manderach explained that confirming the presence of cyclospora on food requires washing large quantities of a suspected product, reducing the resulting runoff, and then testing it for the organism.

"You'd have to have truckloads of lettuce to get to that point," said Manderach, who previously handled cyclosporiasis outbreaks as a food-safety official in Iowa.

Given the scale of the current outbreak, health experts say it is likely there are multiple points of contamination across the food supply, a possibility that further complicates the investigation.

Federal Cuts Add to the Challenge

Several public health experts pointed to reductions at agencies and programs within the U.S. Department of Health and Human Services as an additional obstacle. Health Secretary Robert F. Kennedy Jr. oversaw a series of budget and staffing cuts as part of billionaire Elon Musk's Department of Government Efficiency initiative.

Among the programs affected was the Foodborne Diseases Active Surveillance Network, known as FoodNet, which tracks pathogens including cyclospora, salmonella and listeria. The network scaled back its monitoring to just two pathogens last year, no longer including cyclospora. According to NBC News, the CDC wrote in a memo to the state of Connecticut that funding had not kept pace with the resources required for the program.

Guest, who previously worked at FoodNet, said the loss of that surveillance infrastructure has left investigators without data they once relied on.

"When we see an outbreak or a cluster or something, we don't have the data we normally expect to go back to use to help us, and this is one of those consequences," Guest said. "You're starting in the dark."

The CDC told the BBC it continues to work with 3,000 health departments nationwide to gather data and is still collecting information on cyclospora through surveillance systems other than FoodNet. The department said health funding for foodborne diseases has "remained stable."

At the state level, the impact of the funding changes has varied. In Colorado, which has recorded 90 cases this year, roughly in line with past years, the state health department said it has received less federal funding and has fewer staff available to monitor cases. Hope Shuler, a spokesperson for Colorado's public health department, said the state has had to adjust its operations as a result.

"While our colleagues at the CDC are working hard to support state partners, we have had to adapt to federal changes," Shuler said, adding that the state has continued testing, monitoring and sending data to the CDC.

Manderach said that despite early disruptions, federal food safety agencies have largely returned to their previous level of performance.

"While yes, I do think there were challenges early on, most of those seem to have resolved," he said.

David Weber, a professor of medicine, pediatrics and epidemiology at the University of North Carolina at Chapel Hill, noted that other public health emergencies, including the deadly Ebola outbreak in the Democratic Republic of Congo, have also strained available resources.

Nancy Glick of the National Consumers League said the funding shortfalls have shifted more responsibility onto states.

"States are doing that now, but they don't have the resources that the CDC had," Glick said.

A Time-Consuming Search

To identify the outbreak's source, epidemiologists are now interviewing everyone who has tested positive for cyclosporiasis about what they ate in the one to two weeks before falling ill, working backward in hopes of finding a common product or location tied to the infections.

Weber said the process, while methodologically simple, demands significant staffing that many smaller local health departments struggle to provide.

"It is pretty straightforward, but it takes a lot of person power to do it," he said.

In the meantime, health officials say the public will need to remain vigilant. Guest acknowledged the difficulty many Americans may feel in trying to protect themselves without knowing the outbreak's source.

"At the moment, the list of things that you need to be concerned about is unfortunately quite long, making it feel really hard to control," she said.

With investigations ongoing and no clear source yet identified, officials say the outbreak may continue to grow before health authorities can pinpoint — and shut down — the contamination responsible.