A parasite outbreak linked to lettuce sickened nearly 13,000 people.
Now, FDA investigators have found the parasite where the lettuce was grown and processed.
Two environmental samples collected in Mexico tested positive for Cyclospora, the parasite that causes cyclosporiasis.
One came from a tank holding outgoing wastewater at a Taylor Farms de Mexico processing facility. The other came from a drainage ditch at an iceberg lettuce grower identified during the investigation.
The findings strengthen the link to recalled shredded iceberg lettuce, but they do not establish exactly how the food became contaminated.
The outbreak involved 12,883 cases across 21 states, with 570 hospitalizations and two deaths reported. Both people who died had significant underlying health conditions.
The outbreak is over, and officials say the recalled lettuce is off the market.
Investigators began examining the outbreak in July after illnesses were linked to shredded iceberg lettuce served at some Taco Bell restaurants. Tracing the supply chain led them to Taylor Farms de Mexico and growers in central Mexico.
The company recalled implicated lettuce on July 17. Taco Bell stopped using lettuce from that supplier.
Cyclospora infects the intestines after someone consumes contaminated food or water. Symptoms typically begin about a week later and can include watery diarrhea, stomach cramps, loss of appetite, and fatigue.
Without treatment, illness can persist for weeks or longer, and symptoms may disappear before returning.
Taylor Farms says its central Mexico facility remains closed while it works on enhanced safety procedures. It has also said the independent grower associated with the positive sample is no longer a supplier.
The FDA closed its investigation on October 2.
Finding the parasite in the surrounding environment provides another piece of evidence. The exact route from that environment to the lettuce remains unresolved.
Learn more:
“FDA finds potential source of cyclosporiasis outbreak linked to lettuce.” ABC News