The Taylor Farms shredded lettuce cyclospora test was a false positive, according to the FDA. The test was conducted on July 18, 2026. This does not mean that Taylor Farms lettuce that was imported from Mexico is not the cause of the outbreak in the states of Michigan, Ohio, Indiana, Kentucky, and West Virginia.
Traceback and information from patients has established that Taylor Farms shredded iceberg lettuce that was served at Taco Bell restaurants in those states is probably the source of the pathogen. The FDA has traced the lettuce served at Taco Bell to a single farm in Central Mexico that supplies Taylor Foods. This traceback is solid evidence that the lettuce is most likely linked to the outbreak.
In addition, information from patients also may link the lettuce to the illnesses. In Michigan, the Department of Health and Human Services analyzed food exposure information from 190 of their cases. Those patients said they ate at Taco Bell, and 90% of the respondents said they ate iceberg lettuce. That is strong epidemiological evidence. Taylor Farms de Mexico has recalled all of its iceberg lettuce harvested from Central Mexico from foodservice and retail distribution in the U.S..
Testing for parasites is different from testing for bacteria or viruses for several reasons and is much more difficult. First, the parasites on the food exist in very small numbers. That means the sample size that is tested has to be huge. In addition, parasites do not grow or reproduce on food or on any substrate; they need a human body to reproduce, so scientists cannot reproduce the cyclospora oocyst in order to test it. In addition, the oocysts hide in crevices and rough surfaces on food, so it is very difficult to isolate and remove them for testing.
Many methods for detecting the parasite have viability limits. That means that scientists can’t tell if a parasite they recover from food is capable of causing illness. Finally, testing for parasites is not standardized, and the tools used for mapping the genetic makeup of parasites, most notably whole genome sequencing (WGS), can’t be used on parasites at this time.
The FDA will conduct more testing and will release more information as the results come in. Meanwhile, continue protecting yourself by washing all produce carefully, following recall information, and choosing to cook more foods instead of eating produce raw. And learn the symptoms of cyclosporiasis so if you do get sick you can get tested and treated quickly.
