A sample of lettuce from a supplier that has recalled products as a result of a multi-state cyclospora outbreak produced a false positive result for the parasite, federal officials said Sunday.
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The false positive was discovered when the U.S. Food and Drug Administration re-reviewed the results of a sample from Taylor Farms de Mexico that as reported positive Saturday.
“As of July 19, 2026, there are no confirmed positive sample results for product testing for Cyclospora,” the FDA said in its statement.
The false positive does not change the company’s earlier voluntary recall of its iceberg lettuce that was sourced from central Mexico.
Taylor Farms, which produces lettuce for Taco Bell and multiple grocery retailers, continues “working with the firm to ensure product implicated in this outbreak has been removed from the market,” the FDA said in a statement Sunday evening.
In a statement Sunday night, Taylor Farms said the FDA made a mistake and apologized. It echoed the FDA’s statement and said the FDA has not identified a “single positive product test result for Cyclospora.”
The company said it will continue to work with public health officials investigating the origins of the outbreak.
More coverage of the outbreak
In the FDA’s Saturday notice of the positive test, which it has since removed from its updates on the outbreak, the agency said that product was not part of the existing Taylor Farms recall and that the company was “working to identify whether any part of this implicated lot is available in commerce or in consumers homes.”
The company announced Friday that Taylor Farms de Mexico was voluntarily recalling iceberg lettuce from central Mexico from the U.S. market “because it has the potential to be contaminated with Cyclospora.” The recalled products had been distributed to stores in 27 states, according to the FDA.
The recall came after the FDA zeroed in on the product, which it said had been provided to Taco Bell locations in five states where people ate before being sickened.
The same day, Taco Bell said it would no longer use the producer for its lettuce.
The FDA warned consumers in an alert Friday: “Do not eat shredded iceberg lettuce from Mexico served at Taco Bell locations in Indiana, Kentucky, Michigan, Ohio and West Virginia.”
Nearly 7,000 cases of cyclosporiasis have been confirmed or are under investigation in the U.S. since May 1, according to the Centers for Disease Control and Prevention. The foodborne illness can cause severe watery diarrhea, fatigue or loss of appetite, experts say.
The FDA said Saturday’s positive test was an erroneous result based on false amplification. “The finding does not represent true amplification and should be considered a false positive,” it said.
Amplification creates copies of samples used to investigate pathogens, which can be easier to identify when amplified. According to research in the Annals of Clinical & Laboratory Science, “Amplification-based techniques are now used routinely in clinical laboratories to detect organisms that do not grow in conventional culture media.”
Thomas Gremillion, director of food policy at the Consumer Federation of America, said last week that it is “really hard to grow cyclospora in the lab.”
Donald W. Schaffner, chair of the Department of Food Science at Rutgers University, said Sunday that the Taylor Farms recall was “the right thing” for it to do, regardless of the status of lab tests, and said the FDA showed courage in admitting it was wrong about the positive test.
“Unfortunately testing for this organism is difficult,” he said by email. “False positives are always possible. In this case, I think it may lead to more confusion and uncertainty in the minds of consumers.”
He said regulatory agencies should have to provide more data when announcing positive results, including the false-positive rate.
“I would hope that consumers wouldn’t ignore it,” he said, referring to the false positive, “but realize that the science is complicated.”
