Health officials are still trying to pinpoint the source of a multi-state outbreak linked to a diarrhea-causing parasite, after acknowledging that a suspected food source has tested negative for the pathogen.
The FDA said Sunday that lettuce from produce supplier Taylor Farms, which was identified last week as a possible source of the cyclosporiasis outbreak, had produced a false-positive test result for cyclospora, the parasite responsible for the illness.
Taylor Farms announced Friday that it was recalling lettuce grown in Mexico, following reports that the CDC and FDA were examining shredded lettuce supplied by the company to Taco Bell restaurants in the US as a potential source of the outbreak.
The company said none of its products had been linked to the illnesses. Still, it added that, “based on information provided yesterday by the FDA, Taylor Farms de Mexico is voluntarily removing all iceberg lettuce sourced from central Mexico.”
In its Sunday update, the FDA said a sample of lettuce from the company had initially been reported as positive for cyclospora on July 18.
However, the agency said that “due to the complexity in detection of cyclospora, FDA laboratory experts re-reviewed the sample results and have concluded that the finding does not represent true amplification and should be considered a false positive.”
The FDA added: “FDA has notified Taylor Farms and continues working with the firm to ensure product implicated in this outbreak has been removed from the market. FDA and state partners continue to collect and analyze product samples.
“As of July 19, 2026, there are no confirmed positive sample results for product testing for cyclospora.”
Taylor Farms announced on Friday a recall of its lettuce grown in Mexico (stock image)
Following the FDA’s announcement, Taylor Farms said in a statement on Sunday: ‘Yesterday, FDA informed Taylor Fresh Foods that one of its iceberg lettuce products from central Mexico had a “confirmed positive” test for cyclospora.
‘Today, we were informed that FDA made a mistake, and this was a false positive. To be clear, at this moment, FDA has not identified a single positive product test result for cyclospora.’
No update was given on Taco Bell’s potential role in the outbreak.
On Thursday, the CDC had posted an update to the cyclosporiasis outbreak investigation, stating tracing had linked the illnesses to shredded iceberg lettuce from a single supplier that had been used at Taco Bell restaurants in Indiana, Kentucky, Michigan, Ohio and West Virginia.
Taco Bell issued a statement the same day: ‘Based on ongoing conversations with public health officials, and out of an abundance of caution, Taco Bell has taken immediate action to voluntarily remove potentially impacted lettuce from a supplier in select states.
‘The affected ingredient from our supplier is being indefinitely removed from our supply chain nationwide and will be replaced within 24 hours in select states.
‘While no official advisory has been issued, we believe public health is a shared responsibility among restaurants, their suppliers, and authorities, and we are proud to have consistently acted quickly and proactively to protect our guests.
‘Taco Bell has taken precautionary action, and we encourage all relevant restaurants, retailers, and foodservice operators to do the same.’
Nationwide, cases of cyclosporiasis are estimated to have climbed near 7,000 across more than 40 states.
Not all cases are related to this outbreak and the CDC previously said it is ‘also investigating other outbreaks and illnesses of cyclosporiasis nationally that are unrelated to this outbreak.’
People become infected with cyclosporiasis by eating food or drinking water contaminated with the cyclospora parasite, most commonly through fresh produce such as leafy greens, herbs and berries.
In the US, most cases are typically linked to international travel or imported produce from regions where the parasite is common, including Mexico, Central America, South America and the Caribbean.
Fresh produce can become contaminated if it is washed or irrigated with water contaminated by human sewage.
Previous outbreaks have been linked to bagged salad kits, cilantro, basil and other leafy greens.
Cyclosporiasis typically causes explosive diarrhea, abdominal cramping, nausea, vomiting and fatigue.
Unlike norovirus or routine food poisoning, however, symptoms often come and go rather than resolving after a few days.
Without treatment, experts say the illness can persist for weeks or repeatedly return.
Anyone with diarrhea lasting more than a few days should seek medical care and specifically ask for a cyclospora test, as it is not routinely ordered, Dr Swapnil Patel, vice chair of medicine at Hackensack Meridian Jersey Shore University Medical Center, told the Daily Mail.
The test detects cyclospora DNA in stool samples and typically requires one to three samples.
Treatment for the infection consists of the antibiotic trimethoprim-sulfamethoxazole, sold under the brand names Bactrim, Septra and Cotrim.
