'Explosive diarrhoea' outbreak remains a mystery as officials struggle to find sources

Some public health experts said finding the outbreak's origins also are complicated by cuts to agencies and programmes within the US Department of Health and Human Services (HHS).

Health Secretary Robert F Kennedy Jr made a number of budget and staff cuts as a part of billionaire Elon Musk's efforts to cut costs with his Department of Government Efficiency (Doge).

The federal government reduced the capacity of its Foodborne Diseases Active Surveillance Network (FoodNet), which tracks several pathogens, including cyclospora, salmonella and listeria. FoodNet scaled back monitoring for all but two pathogens last year.

"Funding has not kept pace" with resources required for the programme, the CDC wrote in a memo to the state of Connecticut, according to NBC News.

Before FoodNet stopped monitoring cyclosporiasis, it gathered data about people who tested positive, and tested food sources from states and labs, then collated it at a national level, said Guest, who previously worked at FoodNet.

"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," she said. "You're starting in the dark."

The CDC is still working with 3,000 health departments to gather data and it continues to collect data on cyclospora through surveillance sytems other than FoodNet, HHS told the BBC.

The department said health funding for foodborne diseases has "remained stable".

In Colorado, which has had 90 cases this year - about the same as past years - the state health department said it received less federal funding and has fewer staff to monitor cases.

"While our colleagues at the CDC are working hard to support state partners, we have had to adapt to federal changes," Hope Shuler, a spokesperson for the state's public health department, said.

The state has continued testing, monitoring and sending data to the CDC, she said.

Manderach said that federal agencies in charge of food safety are largely performing to the previous standard despite agency changes during the Trump administration.

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

Other, more serious health problems like the deadly Ebola outbreak in the Democratic Republic of Congo also have strained resources, said David Weber, professor of medicine, pediatrics and epidemiology at University of North Carolina at Chapel Hill.

Shortages put the onus on states to take more responsibility for foodborne illnesses, said Nancy Glick of the National Consumers League.

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