Why the US cyclospora outbreak is difficult to trace

Federal investigators say the cyclospora parasite behind the suspected illnesses of thousands of Americans has been unusually difficult to trace. Experts say it does not leave behind any culturable samples and no genetic fingerprints, which forces officials to rely almost exclusively on patient interviews instead of lab confirmation. 

Additionally, the two-week incubation period further complicates traceback work from the FDA, making it harder for people to pinpoint exactly where and what they ate that potentially led to illness. 

Testing for cyclospora is difficult

What they're saying:

Craig Hedberg, a University of Minnesota food safety expert, said harvest cycles and produce perishability could have already moved the contaminated lettuce through the distribution system. 

"As we’ve seen with this outbreak of Cyclospora, in many instances, those increases will be recognized at a state level before the data gets compiled nationally to allow our federal officials to have a clear picture of what’s going on," Hedberg said. 

Big picture view:

Unlike pathogens such as salmonella or E. coli, which can be sequenced and matched through national databases, cyclospora cannot be traced using those same methods. Scientists have to take genetic material from the organism and make synthetic copies of the DNA, which could lead to a false positive, as we saw in the case with Taylor Farms. 

The CDC urged doctors to start testing for cyclospora to make sure people are treated properly. With the publicity that has been generated by the recent outbreak of cyclospora, experts say more people are likely seeking out testing.

FoodNet reporting for cyclospora became optional in 2025

Dig deeper:

FoodNet is a collaboration between CDC, USDA, FDA and 10 state health departments to track laboratory-confirmed infections caused by eight pathogens commonly transmitted through food. They use the data to help researchers monitor outbreaks in the U.S. and shape food safety policies.  

The backstory:

In July 2025, the FDA made cyclospora tracking optional, removing the parasite from its mandatory surveillance list. The scale back narrowed mandatory reporting to only salmonella and E. coli.

Public health experts say the cuts limited the federal government’s ability to quickly analyze trends and spot early signs of widespread cyclospora outbreaks. 

"FoodNet has no role, really, to play in routinely identifying outbreaks of reportable diseases on the national level," Hedberg said. "It’s really intended to help over time monitor trends in occurrence of these diseases so we can see from year to year whether illnesses are increasing or decreasing—so we can have better estimates for what the burden of illness associated with these pathogens might be." 

What's next:

Hedberg believes we could see cases rise, but it may not reflect a growing trend. "We'll probably see a huge ​influx of new cases, and it doesn't necessarily reflect that the actual outbreak is continuing to grow."

 

 

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