US health officials have said an earlier laboratory test linking iceberg lettuce to a widespread Cyclospora outbreak was incorrect, leaving investigators still searching for the source of an illness that has sickened thousands of people across the country.
The US Food and Drug Administration (FDA) announced on Sunday that it had re-examined an iceberg lettuce sample supplied by Taylor Farms and determined that the previous positive result for the Cyclospora parasite was a false positive. The agency said it had informed Taylor Farms of the updated findings while continuing its investigation into the outbreak.
The revision comes a day after the FDA reported that the lettuce sample had tested positive for the parasite. That initial announcement raised concerns that the contaminated product could have been identified. However, the agency now says further review by laboratory experts showed the test result did not represent a genuine detection of Cyclospora.
Despite the updated laboratory findings, the FDA said it is continuing to work with Taylor Farms to ensure any products believed to be connected to the outbreak have been removed from the market while investigators search for the actual source of the contamination.
The outbreak has led to at least 94 hospitalisations, although no deaths have been reported. Health authorities say infections were first detected on May 13, and the number of confirmed cases has continued to grow in recent weeks.
Cyclospora is a parasite that causes cyclosporiasis, a foodborne illness that can trigger prolonged watery diarrhoea, sudden weight loss, reduced appetite and other digestive symptoms. Officials note that symptoms may not appear until up to two weeks after exposure, making it more difficult to identify contaminated food.
Taylor Farms announced on Friday that it had voluntarily removed all iceberg lettuce sourced from central Mexico from the US market. The company also released a list of affected products as a precaution. The FDA clarified that the lettuce sample initially reported as positive was not part of that voluntary removal.
Unlike a formal recall, a voluntary product removal does not require a company to recover products already in the marketplace, although it is intended to reduce potential risks while investigations continue.
The Centers for Disease Control and Prevention (CDC) has advised consumers not to eat shredded iceberg lettuce served at Taco Bell restaurants in Indiana, Kentucky, Michigan, Ohio and West Virginia. Taco Bell said it has completed the removal of affected Taylor Farms lettuce from restaurants in those states.
Taylor Farms said it has stopped receiving products from the implicated lot, suspended distribution of iceberg lettuce from central Mexico, notified customers and continues cooperating with the FDA, CDC and state health authorities as efforts continue to determine the true source of the outbreak.
