Federal investigators are still focusing on shredded iceberg lettuce from Taylor Farms de Mexico as the most likely source of a major Cyclospora outbreak, despite withdrawing an earlier positive laboratory test as a false positive.
Health officials say there is no evidence that other produce is involved in the five-state outbreak, but they have not ruled out additional foods or distribution channels as the investigation continues.
Because Cyclospora is notoriously difficult to detect in food, investigators are relying primarily on epidemiological evidence and traceback data rather than laboratory testing alone.
Federal health officials continue to investigate this summer's widespread outbreak of illnesses caused by the Cyclospora parasite, saying the evidence still points overwhelmingly to shredded iceberg lettuce supplied by Taylor Farms de Mexico, even after an earlier laboratory finding was determined to be a false positive.
The Food and Drug Administration (FDA) says its investigation remains active, with traceback evidence linking contaminated shredded iceberg lettuce served at Taco Bell restaurants in five states to a single supplier in central Mexico. The agency stressed that the erroneous laboratory result does not change its overall conclusion because the epidemiological evidence remains strong.
The outbreak has sickened at least 1,645 people in Indiana, Kentucky, Michigan, Ohio, and West Virginia, with more than 140 hospitalizations. No deaths have been reported.
Meanwhile, the FDA announced Thursday that it is investigating a new Cyclospora outbreak with 72 new cases. It has not yet identified the source.
Health officials in North Carolina this week said they are investigating cases that may be linked to parsley and cilantro.
False positive complicated the investigation
On July 19, FDA announced that a laboratory sample previously reported as positive for Cyclospora should instead be considered a false positive after experts re-examined the test.
Cyclospora is exceptionally difficult to detect in food samples because the parasite is often present in very low numbers and laboratory testing remains technically challenging. As a result, investigators frequently depend on patient interviews, food histories, and supply-chain tracing to identify the source of an outbreak rather than laboratory confirmation alone.
The FDA says it continues collecting and analyzing product samples, but as of its latest update, no food samples have been confirmed positive for Cyclospora.
Could other produce be contaminated?
For now, health officials are not advising consumers to avoid produce generally. Their warning remains limited to recalled iceberg lettuce and products containing it.
However, investigators have stopped short of declaring that lettuce is the only contaminated food.
The FDA notes that because the investigation is ongoing, "additional implicated brands, restaurants, retailers, or distribution channels may be identified" if new evidence emerges. That reflects standard practice in foodborne illness investigations rather than evidence that another fruit or vegetable has already been implicated.
Cyclospora has historically been linked to a variety of fresh produce, including leafy greens, cilantro, basil, raspberries, and other fruits and vegetables that are eaten raw. The parasite is spread when produce is contaminated by water or soil containing human waste; it cannot multiply once it reaches food.
Recall remains in effect
Taylor Farms de Mexico voluntarily recalled iceberg lettuce sourced from central Mexico and distributed between June 29 and July 16. The recall includes shredded lettuce sold to food-service customers and certain Marketside-branded iceberg lettuce products sold at Walmart stores in 15 states. Taco Bell has also stopped using lettuce supplied by the implicated source.
Consumers should discard any recalled lettuce, avoid eating recalled products served in restaurants, and contact a healthcare provider if they develop prolonged watery diarrhea, stomach cramps, nausea, or fatigue after eating fresh produce. Symptoms can begin several days to two weeks after exposure, and the illness often requires prescription antibiotics for treatment.