Despite a False Test Result, Taylor Farms Is Still Linked to Cyclospora Outbreak

The U.S. Food and Drug Administration (FDA) said on Monday that Taylor Farms, a lettuce company, is still the main focus of an investigation into a widespread cyclospora outbreak. This came after the FDA took back a test result it had announced just one day earlier. The agency had said a sample of lettuce tested positive for the parasite, but then said that result was wrong. Even so, officials say there is still strong evidence linking Taylor Farms to the outbreak.

Cyclospora is a tiny parasite that can make people very sick with stomach cramps, diarrhea, and fatigue. The current outbreak is the largest ever recorded in U.S. history. Taylor Farms had already recalled iceberg lettuce that had been sent to 27 states. However, the company did not give shoppers enough information to know if they had bought the bad lettuce, which caused a lot of confusion.

As people tried to sort out what was happening, health officials in Michigan reported that the number of sick people in their state had jumped to 6,148 on Monday. That was an increase of more than 1,000 cases in just one weekend. Other states also reported more cases, showing the outbreak was still spreading.

Susan Mayne, a former top FDA official and now a professor at Yale University, said it is very unusual for the FDA to announce a test result and then take it back. She worked at the FDA for more than eight years and could not remember a time when something like this had happened before. She said the back-and-forth messaging raised serious questions and was 'most unfortunate.'

Scientists explained why false positive test results can happen with cyclospora. Kalmia Kniel, a microbiologist at the University of Delaware, said cyclospora is 'one of the most difficult pathogens to detect in agricultural products.' She explained that the parasite's eggs, called oocysts, are often present in very small numbers in food samples. Other substances in the food can also confuse the test, or it might accidentally pick up DNA from other tiny organisms that look similar to cyclospora.

Another expert, John Guzewich, said investigators might have tested a part of the lettuce batch where the parasite was simply not present. Cyclospora only grows inside human bodies, so testing human waste is actually the most accurate way to find it. The FDA's main food test is called a PCR test, and while it is the best tool available, it is not perfect.

Investigators also interview sick patients to find out what they ate before they got sick. They look for a common food that all the sick people shared — in this case, lettuce. They then trace that food back to the farm or supplier. Mayne said that in this outbreak, there is a 'robust,' or strong, amount of evidence connecting the patients to Taylor Farms' lettuce.

There is another challenge: the food that caused the illness may already be gone. The contaminated lettuce has likely been eaten or thrown away. The farm fields where the lettuce was grown have probably already been harvested and prepared for new crops, making it very hard to collect a positive test from the original source.

Taylor Farms said in a statement that the FDA had 'not identified a single positive product test result for cyclospora.' Still, based on information from the FDA, the company recalled all iceberg lettuce it sourced from central Mexico. The FDA said its investigation is still ongoing and that lettuce remains the primary suspect.

If Taylor Farms lettuce is truly the main cause of the outbreak, experts say the number of new cases should start to level off soon. Donald Schaffner, a food science professor at Rutgers University, said rising case numbers now likely reflect older cases that are already getting better. However, some experts worry that the back-and-forth messaging from the FDA could make the public trust health officials less, with Mayne saying the flip-flop's impact on trust was her biggest concern.