FDA Reverses Positive Test Finding in Cyclospora Investigation, But Still Says Lettuce Is Behind Outbreak
The U.S. Food and Drug Administration has made a reversal in one of the country’s largest recent foodborne illness investigations, acknowledging that a laboratory test that appeared to detect the Cyclospora parasite in shredded iceberg lettuce was actually a false positive.
Despite the reversal, the agency says its investigation still points to shredded iceberg lettuce supplied by Taylor Farms de Mexico as the source of a multistate cyclosporiasis outbreak that has sickened more than 1,600 people.
The updated position follows several days of rapidly changing developments in the federal investigation. On July 18, the FDA reported that one sample of shredded iceberg lettuce supplied by Taylor Farms had tested positive for Cyclospora cayetanensis, the microscopic parasite that causes cyclosporiasis.
However, after conducting an additional laboratory review, agency scientists concluded the result did not represent a true detection. “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 agency said in its updated investigation notice.
Cyclospora cayetanensis is a microscopic parasite that causes cyclosporiasis, an intestinal illness characterized by prolonged watery diarrhea, stomach cramps, nausea, fatigue, loss of appetite, and weight loss. Symptoms typically begin about a week after consuming contaminated food or water and, without treatment, can persist for weeks or even months.
According to federal investigators, Taco Bell has voluntarily stopped using lettuce supplied by the implicated source and has begun replacing the ingredient throughout its restaurants. The company said the action was taken out of an abundance of caution while the investigation continues.
The CDC has confirmed 1,644 illnesses linked to the outbreak, including 94 hospitalizations. No deaths have been reported. Health officials have also identified thousands of additional suspected cases nationwide that remain under investigation, making this one of the largest documented Cyclospora outbreaks in U.S. history.
The FDA also confirmed that, as of July 19, investigators had not identified any confirmed positive product samples for Cyclospora. Even so, regulators stressed that the mistaken laboratory result does not change the overall findings of the investigation.
Still, the agency said that extensive traceback and epidemiological evidence, rather than the withdrawn laboratory result, continues to point toward shredded iceberg lettuce distributed by Taylor Farms de Mexico from central Mexico.
Federal investigators traced illnesses reported by customers at Taco Bell restaurants in Indiana, Kentucky, Michigan, Ohio and West Virginia to a common supplier of shredded iceberg lettuce. The FDA said that convergence during its traceback investigation remains the strongest evidence supporting the current recall.
The agency continues to advise consumers not to eat recalled iceberg lettuce from Taylor Farms de Mexico and says restaurants and retailers should immediately discard affected products. The recalled lettuce was distributed between June 29 and July 16 across 27 states and includes certain Marketside-branded iceberg lettuce products sold at Walmart, along with food service products supplied to restaurants.
Taylor Farms said it voluntarily removed all iceberg lettuce sourced from central Mexico after receiving the FDA’s initial findings. Following the agency’s reversal, the company said it had been informed the original laboratory result was incorrect.
“To be clear, at this moment, FDA has not identified a single positive product test result for Cyclospora,” the company said, adding that it had completed the recall “out of an abundance of caution.” Taylor Farms also stated that the FDA apologized for the erroneous laboratory finding, although the agency has not publicly confirmed issuing an apology.
The investigation remains active as FDA and state health officials continue collecting and testing additional lettuce samples in an effort to identify definitive microbiological evidence linking the parasite to the contaminated produce.
Because Cyclospora cannot be cultured in laboratories and is notoriously difficult to detect in fresh produce, investigators often rely heavily on epidemiological interviews and supply chain traceback rather than laboratory confirmation alone.
According to the Centers for Disease Control and Prevention, the outbreak under investigation represents a subset of a much larger national increase in cyclosporiasis cases this summer. The illnesses linked to the Taco Bell investigation involve people who reported eating shredded iceberg lettuce before becoming sick.
