Cyclospora investigation still points to recalled lettuce, FDA says

The FDA said Monday it still thinks Taylor Farms lettuce is likely behind a Cyclospora outbreak, even after pulling back earlier test results linking the produce to the parasite.Why it matters: Tracking the source of the diarrhea-causing illness presents a steep challenge for health officials and suppliers, while news of a false positive risks confusing consumers about which recalled products to avoid.At least 1,644 people have fallen ill, though officials believe the true number is likely much higher. Taylor Farms has voluntarily recalled shredded iceberg lettuce sourced from central Mexico in connection with the outbreak.The big picture: Laboratory results are only one piece of foodborne outbreak investigations, which also rely on tracing illnesses and food shipments.The sample that was initially flagged as positive over the weekend — before the FDA walked back that determination — was not part of the current recall, acting Deputy Commissioner for Food Donald Prater explained in a Monday call with reporters.The sample's re-evaluation "does not alter the data supporting the outbreak advisory that prompted the current voluntary recall," he added.The Centers for Disease Control and Prevention is still advising people to avoid recalled products — including at Taco Bell, which says it has removed the affected lettuce from its restaurants.Catch up quick: The FDA turned heads with its update that a sample of Taylor Farms lettuce from Mexico that had originally tested positive for Cyclospora was re-reviewed and "should be considered a false positive."Taylor Farms said in a social media statement that the "FDA apologized to us" and that the agency had "made a mistake."However, in a post, the FDA clarified that its traceback investigation of the surge in cases was still converging on shredded iceberg lettuce from Taylor Farms locations in central Mexico. An FDA official said Monday that while the agency provided information to explain the circumstances to Taylor Farms, which produces salads and other produce, it did not offer an official apology.Between the lines: FDA officials have stressed that it's challenging to track Cyclospora in food, noting restrictions like the short shelf-life of fresh produce and the lengthy incubation period before symptoms show up."Test results are difficult to obtain, and most of the time, our traceback and epidemiologic information are what allows us to determine the source of the outbreak," Prater explained.What we're watching: Acting FDA Commissioner Kyle Diamantas stressed Monday that the investigation is ongoing, "including into other potential sources and commodities for other clusters of illnesses." Go deeper: Gut-wrecking stomach bug mysteriously surges in U.S.