Test that found source of US explosive diarrhoea outbreak was false positive

What the report says

BBC World News reported that US Food and Drug Administration officials have withdrawn an earlier finding that appeared to identify cyclospora in an iceberg lettuce sample connected to a major cyclosporiasis outbreak. The FDA had said on Saturday that a sample from Taylor Farms, a supplier to Taco Bell, tested positive for the parasite, but said Sunday that specialists re-examined the result and determined it was a false positive. As a result, the precise source of contamination remains unidentified.

The outbreak has sickened thousands of people in the US, according to the BBC’s account, with no deaths reported and at least 94 hospitalizations. The FDA said infections were first detected on 13 May. Cyclospora can cause watery diarrhoea lasting for days, appetite loss and sudden weight loss, and symptoms may not appear for up to two weeks after exposure.

Taylor Farms had already moved to remove all iceberg lettuce sourced from central Mexico from the US market and listed affected products. The company said it stopped receiving product from the implicated lot, suspended distribution of the lettuce, notified customers and was continuing to work with federal and state authorities. Taco Bell said it had completed removal of affected Taylor Farms lettuce from its restaurants.

The CDC has advised consumers not to eat shredded iceberg lettuce served at Taco Bell sites in Indiana, Kentucky, Michigan, Ohio and West Virginia. The FDA also said the lettuce recall covered 27 states and included Marketside-branded iceberg lettuce sold at Walmart locations in 15 states. The false-positive update matters because public health agencies are still investigating how the parasite entered the food supply while removal and recall actions continue.