By Julie Steenhuysen and Kamal Choudhury
Oct 2 (Reuters) – The US Food and Drug Administration said on Friday it has concluded its investigation into the largest recorded multistate outbreak involving the cyclospora parasite, saying there was strong evidence of a link to recalled shredded iceberg lettuce from Taylor Farms’ Mexico subsidiary.
The outbreak, which sickened thousands, prompted one of the largest food recalls in recent years and renewed scrutiny of food-safety controls for imported produce.
FDA said its investigation could not definitively determine how the contamination happened, but two samples showed cyclospora was present in the environment where lettuce was grown and processed.
One sample was found in a tank that held outgoing wastewater at Taylor Farms de Mexico’s processing facility and the other was in a drainage ditch at an iceberg lettuce grower, it said.
A spokesperson for parent company Taylor Fresh Foods said, “The independent grower where a positive sample was found is no longer part of our supplier program. The sample FDA referenced came from discharged waste and sewer water outside of our processing facility.
“As FDA noted in its report, there is currently not enough evidence to conclusively determine how contamination occurred or how results for these samples relate to ongoing genotyping of clinical specimens,” the spokesperson said, referring to the FDA’s statement that it intends to match the samples with those taken from patients sickened in the outbreak.
The summer-long outbreak rattled consumer confidence, with some shoppers avoiding raw fruits and vegetables as well as dining out, and hurt foot traffic at restaurants such as Taco Bell, Sweetgreen and Chipotle.
FDA CHANGES
The FDA said it is continuing to carry out post-outbreak activities, including looking into the root cause, and laid out a 10-point plan to strengthen US surveillance efforts and mitigate future outbreaks of the parasite.
Patient illness reports and supply-chain tracking strongly supported the link between the recalled lettuce and the multistate outbreak, which caused intestinal sickness, the FDA said.
Genetic testing of both positive samples is complete, and the regulator is still analyzing how the results compare with ongoing testing of samples from patients.
Bill Marler, a lawyer specializing in foodborne illness, said it will be critical to learn whether the genotypes, or genetic profiles, from the two samples match the parasites taken from people sickened in the outbreak.
The end of the FDA’s investigation reflects that officials cannot do much more to trace the source of the outbreak, said Craig Hedberg, a University of Minnesota food safety expert.
The two positive samples that FDA reported tie in with the epidemiology from the main part of the outbreak over the summer, Hedberg said.
“It is all consistent with the picture that emerged over the course of the summer, with the bulk of the outbreak-associated cases being tied with lettuce that was coming up from Mexico,” he said.
The Centers for Disease Control and Prevention declared the outbreak over on September 11. Some 12,883 people across 21 states fell ill after consuming contaminated lettuce, 570 people were hospitalized and two died.
The iceberg lettuce outbreak accounted for more than half of the 19,883 laboratory-confirmed US cyclosporiasis cases reported since May 1. That tally far outpaced 2025, in which 1,180 cases were reported in the United States between May 1 and August 31.
The FDA said senior agency officials met with Mexican public health and agricultural authorities on September 8 to discuss ways to strengthen prevention efforts as part of a 2020 U.S.-Mexico food safety partnership.
To prevent similar outbreaks ahead of the 2027 growing season, the FDA said it will increase monitoring of produce historically linked to the parasite, conduct outreach to growers and issue an outbreak investigation report that will include prevention recommendations.
Marler said that for the 2027 growing season, the agency should adopt a water test that looks for the waterborne parasite and provide access to supplier records within 24 hours of an outbreak. He said the FDA should also establish a proactive inspection schedule for Mexican growers in advance of any outbreak and critically, answer for the thousands of cases of cyclosporiasis not tied to any food.
(Reporting by Julie Steenhuysen in Chicago and Kamal Choudhury in Bengaluru; Additional reporting by Tom Polansek in Chicago; Editing by Shilpi Majumdar and Rod Nickel)
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