US Health Officials Say Earlier Positive Test for Parasite Behind Explosive Diarrhea Outbreak Was False

The U.S. Food and Drug Administration (FDA) announced that a previous positive test for the cyclospora parasite in a sample of iceberg lettuce from supplier Taylor Farms was a false positive. The sample was taken from a product not part of Taylor Farms' voluntary market removal announced on Friday. On Saturday, the FDA reported the positive result, but after re-review on Sunday, it concluded the finding was not a true amplification and should be considered a false positive.

The cyclospora outbreak has infected thousands of people across at least five states, with no deaths but at least 94 hospitalizations. Symptoms can take up to two weeks to appear and include watery diarrhea lasting several days, sudden weight loss, and loss of appetite.

Taylor Farms voluntarily removed all iceberg lettuce sourced from central Mexico from the U.S. market on Friday and issued a list of affected products. A recall differs from voluntary removal in that it requires a company to notify customers and recover products, making it broader and costlier. The FDA said the sample was collected during targeted surveillance of imports as part of its investigation.

The Centers for Disease Control and Prevention (CDC) advises against eating shredded iceberg lettuce served at Taco Bell locations in Indiana, Kentucky, Michigan, Ohio, and West Virginia. Taco Bell confirmed it has completed removal of affected Taylor Farms lettuce from its restaurants. Taylor Farms stated it has stopped receiving product from the implicated lot, suspended distribution of iceberg lettuce from central Mexico, notified customers, and continues working with the FDA and CDC.

The lettuce was recalled in 27 states, including Marketside-branded iceberg lettuce sold at Walmart in 15 states. The exact source of the parasite remains unknown.