US investigators traced a parasite outbreak to shredded iceberg lettuce supplied to Taco Bell restaurants, according to the US Centers for Disease Control (CDC).

The CDC has identified 1,645 people in five states linked to the Taco Bell outbreak so far. 

Health officials identified a single supplier of iceberg lettuce from Mexico as the likely source of the contamination. The supplier distributed lettuce to Taco Bell locations in Indiana, Kentucky, Michigan, Ohio and West Virginia.

Taco Bell, on its part, said it had removed the lettuce from its restaurants.

Authorities did not initially name the supplier, but Taylor Farms later said testing by health officials pointed to "a specific independent farm” that is associated with the company.

The company added that it was "voluntarily removing all iceberg lettuce sourced from central Mexico."

Officials investigate possible additional sources

According to the CDC, authorities were also working to determine whether contaminated shredded iceberg lettuce remains on the market.

Health officials also warned that the investigation was ongoing and that other "brands, restaurants, retailers, or distribution channels” could still be connected to the cyclospora outbreak.

The latest cyclospora outbreak is the largest in recent years, with 30 states having recorded infections this year. 

Michigan has reported particularly high case numbers, with state authorities recording around 5,000 infections. Federal officials have noted that state and federal totals may differ due to reporting standards and processing times.

What is cyclospora, the diarrhea-inducing parasite?

Cyclospora is a foodborne parasite that commonly causes diarrhea "with frequent and sometimes explosive bowel movements,” according to the CDC.

The illness is rarely life-threatening and is generally treated with antibiotics.

Bagged salad mixes and other fresh produce — including from Taylor Farms — have led to cyclospora outbreaks in the past.

Will the cyclospora outbreak impact business?

The outbreak comes at a time when Taco Bell had been posting strong business results. Sales at restaurants open for at least a year rose 8% in the first quarter, and the chain has been preparing further expansion in Europe, including plans to enter Germany and Poland by late 2026.

But in the past, foodborne illness outbreaks have hurt chains by undermining consumers' confidence.

After an E. coli outbreak linked to McDonald's food in 2024, its sales tumbled by 1.4% in the last quarter of the year. The company had previously recorded growth.

"The recent outbreak will ⁠likely dent (Taco Bell's) near-term same-store sales growth," said Ari Felhandler, an analyst at Morningstar.

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Edited by: Sean Sinico