False Positive Test Casts Doubt Over Source of US Cyclospora Outbreak

Mon Sep 14 2026 09:32:11 GMT+0000 (Coordinated Universal Time)

The FDA confirms an earlier positive Cyclospora test on Taylor Farms lettuce was false, keeping the real source of the outbreak unresolved.

US health officials have announced that a positive Cyclospora test on an iceberg lettuce sample from Taylor Farms was a false positive, leaving the true source of the explosive diarrhoea outbreak unclear. The FDA re‑examined the sample during a targeted import surveillance and concluded the detection did not represent true amplification. Taylor Farms has recalled contaminated lettuce from central Mexico and Taco Bell has removed the product from menus, but the outbreak remains linked to Cyclospora that has infected at least 94 people nationwide. The CDC continues to advise consumers against eating shredded iceberg lettuce from select Taco Bell locations while authorities search for the contamination source.

View of Taylor Farms building with trucks

False Positive Test Casts Doubt Over Source of US Cyclospora Outbreak

Tests of an iceberg lettuce sample for the parasite that has caused an explosive diarrhoea outbreak affecting thousands of people in the US produced a false positive, officials have now said.

The Food and Drug Administration (FDA) first reported on Saturday that a sample from food supplier Taylor Farms—known for supplying salad products to the Taco Bell chain—had tested positive for Cyclospora. However, the lab’s re‑review on Sunday confirmed the result was a false positive and the company has been notified.

The outbreak, first detected in mid‑May, has infected at least 94 people and hospitalised 94, but no deaths have been reported. The CDC has linked the parasite to iceberg lettuce sold at Taco Bell locations in five states and advises consumers to avoid shredded lettuce from the chain.

Taylor Farms voluntarily removed iceberg lettuce from central Mexico and issued a list of affected products. Taco Bell confirmed the removal of the implicated lettuce from all restaurants. The FDA’s report declined that the positive sample came from the recalled lot, and the true source of the parasite remains unknown.

Consumers can stay updated by following FDA and CDC alerts and practising careful washing and handling of leafy greens.