Lettuce Sold In MI Provided 'False Positive' For Parasite, FDA Says

Federal officials are still searching for the source of a multistate diarrhea parasite outbreak after a lettuce sample provided a "false positive," the FDA said Sunday.

Taylor Fresh Foods voluntarily recalled some of its products last week after federal officials said a lettuce sample from Taylor Farms de Mexico came back positive for Cyclospora, a bacteria linked to an illness that can cause relentless watery diarrhea.

The FDA said it made a mistake during testing.

"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," officials said in a statement.

Despite the false positive, Taylor Fresh Foods, the parent company of Taylor Farms in California, is still recalling its iceberg lettuce that was sourced from central Mexico.

Officials said Taylor Farms, which produces lettuce for Taco Bell and multiple grocery retailers, is "working with the firm to ensure product implicated in this outbreak has been removed from the market."

The recall came after the FDA focused on lettuce served at multiple Taco Bell locations across five states, including Michigan.

Taco Bell quickly announced it would stop serving the lettuce.

FDA investigators tied 1,644 cyclosporiasis cases in Michigan, Indiana, Kentucky, Ohio and West Virginia to food from Taco Bell from May 13 to July 13.

"Ingredient-level analyses on meals eaten by these cases indicate that 90 percent of those interviewed reported eating iceberg lettuce," FDA officials said.

Michigan health officials also believe lettuce and other salad mixes are tied to the outbreak, but have not yet identified an exact source.

As of Monday, there have been no statewide recalls connected to the outbreak.

The parasitic gastrointestinal illness has infected 5,002 people with 102 hospitalizations in Michigan — and thousands of others nationally.

The Michigan cases have been found in 55 counties with major hotspots in the middle and southeast portions of the state.

Michigan health officials said the state's case numbers alone likely make it the largest cyclosporiasis outbreak in U.S. history.