US health authorities are continuing to investigate the source of the Cyclospora outbreak, which causes diarrhea, after a review of tests showed that the suspected lettuce was not the source of the infection.
The U.S. Food and Drug Administration (FDA) announced on Sunday that a re-analysis of a sample of "Iceberg" lettuce supplied by Taylor Farms proved that the initial test gave a false positive result, confirming that as of July 19, 2026, no confirmed infection had been found in the products that underwent testing.
The administration explained that the sample had shown an initial positive result for the Cyclospora parasite on July 18, but laboratory experts reassessed the results due to the difficulty in detecting the parasite, and concluded that the laboratory signal did not represent a real presence of the parasite.
The administration confirmed that it had informed Taylor Farms of the new findings and is continuing to work with local authorities to collect and analyze additional samples as part of the ongoing investigation to determine the true source of the outbreak.
Taylor Farms announced last Friday that it was recalling its iceberg lettuce products grown in Mexico, after reports indicated that health authorities were investigating the shredded lettuce supplied by the company to Taco Bell restaurants as a possible source of infection.
The company said the recall was a precautionary measure based on information it received from the Food and Drug Administration at the time, stressing that none of its products had been linked to the outbreak.
After the administration announced that the test result was incorrect, the company clarified that the authorities have not yet identified any product that has been proven to be contaminated with the Cyclospora parasite.
Health authorities have not issued any new update on the possible role of the Taco Bell restaurant chain in the outbreak, although the Centers for Disease Control and Prevention (CDC) had previously announced that contact tracing linked cases to a cut of iceberg lettuce used in several branches of the chain in Indiana, Kentucky, Michigan, Ohio, and West Virginia.
Following this, Taco Bell announced the removal of all potentially contaminated lettuce from one of its suppliers in the affected states, and precautionarily withdrew this ingredient from its nationwide supply chain pending the completion of investigations.
It is estimated that around 7,000 cases of Cyclospora have been recorded in more than 40 US states, but authorities confirm that not all of these cases are related to the current outbreak, as other separate outbreaks are also being investigated.
The Cyclospora parasite is transmitted through the ingestion of contaminated food or water, and is most commonly associated with fresh produce such as leafy greens, herbs, and berries. In the United States, most infections are linked to travel to areas where the parasite is prevalent or to the consumption of imported produce from Mexico, Central America, South America, and the Caribbean.
The disease causes diarrhea and abdominal cramps, in addition to nausea, vomiting and fatigue. The symptoms may last for weeks or recur if the patient does not receive appropriate treatment.
Dr. Swapnil Patel, vice chair of medicine at Hackensack Meridian Jersey Shore Medical Center, said that people with diarrhea that lasts for several days should request a Cyclospora test, as it is not usually included in routine checkups.
Diagnosis is based on detecting the parasite's DNA in stool samples, while treatment is usually done using the antibiotic trimethoprim-sulfamethoxazole, which is marketed under several trade names, including Bactrim, Septra, and Cotrim.
