Taco Bell has removed shredded iceberg lettuce from its restaurants after US health authorities linked the ingredient to a multistate outbreak of cyclospora, a parasitic infection that causes prolonged diarrhoea and other gastrointestinal symptoms.
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The fast-food chain told the BBC it took the step "out of an abundance of caution" following discussions with public health officials, adding that the affected lettuce has been removed from its supply chain nationwide.
The company said the product will be replaced, but did not identify the supplier involved.
The US Food and Drug Administration (FDA) has advised consumers not to eat menu items containing shredded iceberg lettuce served at Taco Bell outlets in Indiana, Kentucky, Michigan, Ohio and West Virginia, where the investigation has been focused.
Over 1,600 infections, 94 hospitalisations reported
According to the US Centers for Disease Control and Prevention (CDC), the outbreak has sickened at least 1,644 people, with 94 hospitalisations reported so far. No deaths have been recorded.
Health officials cautioned that the actual number of infections could be significantly higher because many people with mild symptoms may not seek medical care or undergo testing.
Cyclospora infections typically appear two to three weeks after exposure, making outbreaks particularly difficult to trace.
Investigation traces source to Mexico farm
After interviewing hundreds of patients and reviewing their food histories, investigators identified shredded iceberg lettuce served at Taco Bell as the common ingredient among many cases.
The FDA's traceback investigation linked the contaminated lettuce to a supplier sourcing produce from central Mexico. US media identified the supplier as Taylor Farms, though Taco Bell did not name the company.
Taylor Farms said it has voluntarily removed all iceberg lettuce sourced from central Mexico from the US market, adding that federal investigators had traced the outbreak to one of its independent farms, which it said accounts for less than 1 per cent of the country's iceberg lettuce supply.
The company also clarified that none of its branded salad kits or packaged salads are linked to the outbreak.
Symptoms can take weeks to appear
Cyclospora is a parasite spread through contaminated food or water. Unlike many food-borne illnesses, symptoms may not develop until around two weeks after infection.
Common symptoms include watery diarrhoea lasting several days, stomach cramps, loss of appetite, nausea, fatigue and sudden weight loss.
Experts say tracing the parasite is especially challenging because of its long incubation period and the complexity of tracking contaminated produce through supply chains.
Ripple effect hits food industry stocks
The health scare has also rattled investors. Shares of Taco Bell parent Yum Brands fell nearly 7 per cent over the past week as the outbreak investigation gathered pace.
Other restaurant chains with significant fresh produce offerings also came under pressure. Sweetgreen shares dropped sharply earlier in the week before rebounding after the CDC did not identify its ingredients as part of the outbreak. Cava also saw a smaller decline before recovering.
Sweetgreen said it does not use iceberg lettuce in its menu, while Chipotle stated that it does not serve shredded iceberg lettuce and does not believe its ingredients are connected to the outbreak.
The FDA is continuing to investigate whether lettuce from the same supplier was distributed to other restaurants or retailers beyond Taco Bell.
While officials have identified the likely source, the investigation into the broader distribution network remains ongoing.
