A false positive test for Cyclospora in iceberg lettuce linked to a U.S. outbreak has been retracted, leaving the source of the parasite still unknown. At least 94 people were hospitalized, with no deaths reported, according to the FDA and CDC.
The U.S. Food and Drug Administration (FDA) confirmed that a test identifying the parasite Cyclospora in iceberg lettuce from Taylor Farms—supplied to Taco Bell—was a false positive, reversing an earlier finding that had raised alarm about the outbreak’s source.
False Positive Reversal
The FDA initially reported a positive test result for Cyclospora in a sample from Taylor Farms on Saturday, but retracted the finding on Sunday after lab experts reviewed the data. 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 stated. This reversal left the exact origin of the parasite in the outbreak unresolved.
The infections were first detected on May 13, according to the FDA. Symptoms of cyclosporiasis, a parasitic infection, include watery diarrhea, weight loss, and loss of appetite, with onset delayed up to two weeks after exposure. The CDC has advised against eating shredded iceberg lettuce at Taco Bell locations in Indiana, Kentucky, Michigan, Ohio, and West Virginia.
Voluntary Removal and Recall Differences
A recall requires a company to notify customers and recover affected products, making it a broader and more costly corrective action than a voluntary removal. The FDA collected the sample during targeted surveillance of imports as part of its investigation into the outbreak, which has affected thousands of people across at least five states.
Ongoing Investigations and Uncertainties
Despite the false positive, the FDA and CDC continue to investigate the outbreak’s source. The exact source of the parasite is still not known,
the agency said.
Industry and Public Health Implications
The FDA’s surveillance efforts have focused on lettuce from central Mexico, where the affected products were sourced. The agency has not yet determined whether other suppliers may be involved, but its investigation remains ongoing.
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