The US Food and Drug Administration (FDA) announced on Monday, July 20, that the trace-back investigation into the Cyclospora outbreak has pinpointed the source of the epidemic to the shredded iceberg lettuce supplied by “Taylor Farms” in central Mexico.
The FDA stated that there is “convincing epidemiological data” supporting this voluntary recall action.
On Monday, the agency posted on the social platform X, expressing confidence in identifying the source of the related cases at Taco Bell restaurants, owned by Yum Brands in Michigan and four other states, to the shredded iceberg lettuce produced at Taylor Farms’ central Mexico facility.
Last Saturday, the FDA announced that a lettuce sample tested positive for Cyclospora parasite during border inspections of products from “Taylor Farms de Mexico”. However, on Sunday, after laboratory experts reviewed the findings, the FDA indicated that this result should be considered a false positive.
According to data from the Centers for Disease Control and Prevention (CDC), Cyclospora infection is a gastrointestinal illness typically contracted by consuming food (mainly fresh fruits and vegetables) or water contaminated with feces.
Former FDA commissioner Scott Gottlieb stated on Monday that the false positive result does not undermine the FDA’s conclusion as investigators primarily rely on epidemiological evidence rather than laboratory test results.
Gottlieb said, “The false positive test results were for samples collected recently. Therefore, this does not concern the products that triggered the outbreak – the implicated products entered the supply chain three weeks ago.”
“The fact that they (FDA) lack evidence of positives does not mean evidence of absence,” former FDA food safety center director Susan Mayne told The Washington Post in a text message on Monday.
Deciphering many outbreaks relies on basic epidemiological investigations: interviewing patients, tracing their dietary intake, and identifying connections among those infected. Laboratory testing is just a part of a broader analysis.
Rutgers University food scientist Don Schaffner explained to The Washington Post that the method for detecting Cyclospora involves chemical reactions to amplify the DNA in the sample. If parasites are detected after several rounds of testing, it indicates high levels. However, the reliability of this conclusion decreases with additional testing, which can potentially lead to false positives.
Michigan health officials reported 6,148 cases related to the current outbreak on Monday, an increase of 1,146 cases from the previous Friday. There are 102 patients hospitalized in the state, with no reported deaths.
Taylor Farms spokesperson Mindi Mayhew released a statement on Sunday night, stating the completion of the voluntary recall of iceberg lettuce from central Mexico. She emphasized that this recall only applies to iceberg lettuce grown and processed in central Mexico.
Mayhew reiterated that all other Taylor Farms products, including those currently on the market under the Taylor Farms brand, are not involved in this recall. “As the investigation into this outbreak continues, we are committed to working closely with public health authorities.”
Taylor Farms initiated the recall process last Friday; a few hours earlier, the company had announced the voluntary removal of iceberg lettuce from central Mexico from the US market.
Unlike mere voluntary holds or removals of products, recalls require companies to actively notify customers and retrieve affected products from distribution channels, making it a broader and more costly response measure.
Late last Friday, Taylor Farms de Mexico released a detailed recall list covering 27 states, including all iceberg lettuce distributed from central Mexico between June 29 and July 16.