U.S. cyclosporiasis outbreak becomes worst on record, CDC data show

The United States is in the middle of its worst recorded outbreak of cyclosporiasis, a parasitic intestinal illness spread mainly through contaminated produce, according to surveillance data the Centers for Disease Control and Prevention updated on Monday. Since May 1, the agency has logged 19,595 laboratory-confirmed cases acquired inside the country — more than sixteen times the 1,180 cases reported over the same stretch last year.

The tally, current through September 8, includes 1,043 hospitalizations and two deaths. It surpasses the previous single-season high for cyclosporiasis in the United States, an outbreak tied to imported raspberries that topped out at roughly 1,500 illnesses. Most of this year's cases stem from a multistate outbreak linked to iceberg lettuce grown in central Mexico, though federal investigators say a substantial share come from separate clusters whose sources have not yet been identified.

The numbers

Cases have been reported in 49 states and the District of Columbia, according to the CDC. The median age of those sickened is 46, with ages ranging from 1 to 99, and 56 percent are female. The median date of symptom onset was July 8, roughly in the middle of what the agency designates as cyclosporiasis season, which runs from May through August.

Because it typically takes about six weeks from the onset of symptoms for a case to be confirmed and reported to the CDC, the current count is almost certainly an undercount of the season's true toll. The agency's data page notes an additional 9,355 laboratory-confirmed cases still being reviewed to determine whether they were acquired domestically, plus at least 6,149 more that are either not yet lab-confirmed or awaiting patient interviews. Combined, those pending cases could roughly double the confirmed total once fully processed.

The single largest identified driver is a multistate outbreak traced to iceberg lettuce processed by Taylor Farms de Mexico. As of the CDC's most recent update on that investigation, it accounts for 11,458 illnesses across 20 states, 495 hospitalizations and both of the season's confirmed deaths, which occurred in Michigan in patients with underlying health conditions. The gap between that outbreak's count and the national total reflects, in part, the other clusters CDC and the Food and Drug Administration are still working to trace.

How the outbreak grew

Illnesses connected to the lettuce began appearing in mid-June, according to the FDA's outbreak investigation page, well before health officials had identified a common source. Taylor Fresh Foods, the U.S. distribution arm, issued a voluntary recall of the lettuce on July 17, covering Marketside-brand iceberg salad and shredded lettuce sold at Walmart as well as supply used by Taco Bell locations in several states. By the time the recall was announced, the FDA has said, most of the illnesses tied to the product had already occurred, and the best-by dates on the recalled lettuce have since passed.

Cyclospora cayetanensis, the single-celled parasite responsible for the illness, is spread when people ingest food or water contaminated with feces containing its oocysts, most often through fresh produce that is eaten raw. It cannot be passed directly from person to person. In a health alert sent to clinicians in July, the CDC advised doctors to specifically request Cyclospora testing on stool samples, since routine parasite exams often miss it, and noted that a course of the antibiotic trimethoprim-sulfamethoxazole is the standard treatment for patients with normal immune function.

A strained response

The scale of this year's outbreak has drawn attention to the condition of the food-safety system tasked with containing it. Federal funding cuts implemented last year sharply reduced grants that states rely on to run foodborne-illness surveillance, and public health officials interviewed by NPR in August said the effects were visible in the response to the lettuce outbreak. Kentucky's health cabinet told the network its food-safety staff was down 30 to 50 percent; Ohio said its response was unaffected; Michigan, which recorded the season's highest caseload, said it had preserved its surveillance capacity after successfully challenging grant cuts in court.

"I think that that has really pushed us into a new level of vulnerability in terms of our food safety system," said Susan Mayne, who led the FDA's Center for Food Safety and Applied Nutrition until three years ago, describing the cuts to staff who coordinate outbreak response with counterparts in Mexico and other countries.

In a statement to NPR, the Department of Health and Human Services said staff who liaise with foreign food-safety regulators had since been reinstated. The FDA said separately that it "continues to work with federal, state and international partners to investigate these outbreaks" and deploys personnel "where they have the greatest public health impact." A tracking report from the University of Minnesota's Center for Infectious Disease Research and Policy has documented the case count climbing in installments of several thousand at a time as more state reports come in, a pattern epidemiologists say reflects both the outbreak's genuine size and the lag built into the reporting system.

Who is affected, and what comes next

Because the contaminated lettuce moved through national food-service and retail supply chains, illnesses have surfaced far from where the produce was grown or processed, with cases confirmed in nearly every state. People who are pregnant, elderly or immunocompromised face the greatest risk of severe illness, though the CDC's data show cases spanning every adult age group and both sexes in roughly comparable proportions.

The recalled lettuce is no longer on shelves, and the CDC has said the products' shelf lives have long since expired, meaning the immediate exposure from that specific recall has passed. But the agency is continuing to investigate additional Cyclospora clusters whose sources remain unidentified, and has said it will issue further outbreak notices if a common source is confirmed and there is action for consumers to take. Because rinsing produce under running water does not reliably remove Cyclospora oocysts, the CDC's guidance recommends cooking produce to at least 158 degrees Fahrenheit when contamination is a concern, alongside standard food-safety practices.

Cyclosporiasis season formally ends August 31, and new domestically acquired infections are expected to taper off in the coming weeks. But given the six-week reporting lag built into the surveillance system, the CDC has said it expects to keep revising the season's total upward well into the fall, meaning the final case count for 2026 will not be known for some time.