The U.S. Food and Drug Administration has identified a shredded iceberg lettuce supplier as the source of a cyclosporiasis outbreak that has infected more than 400 Americans, officials announced Thursday. Taco Bell, one of the chain's whose menu items have been linked to illnesses, removed lettuce from its locations as a precautionary measure while the investigation continues.

Cyclosporiasis is a parasitic intestinal illness caused by the microscopic organism Cyclospora cayetanensis. Symptoms typically include watery diarrhea, loss of appetite, stomach cramps, nausea, and fatigue. The illness can last for weeks or longer if untreated, though it is rarely fatal and is treatable with antibiotics.

The FDA named the specific supplier responsible for the contaminated lettuce, marking a significant development in what has become one of the larger foodborne illness outbreaks in recent years. Investigators have been working to trace the parasite back through the supply chain since cases began clustering around consumers who reported eating at Taco Bell locations.

The outbreak has grown large enough to prompt a response from the White House, which addressed the situation publicly as the case count rose above 400. Health officials have encouraged anyone who ate shredded lettuce at Taco Bell in recent weeks and is experiencing gastrointestinal symptoms to consult a physician, as early treatment with antibiotics significantly reduces the duration of illness.

Food safety experts noted that Cyclospora outbreaks in the United States have historically been linked to fresh produce, including cilantro, raspberries, and various leafy greens, often traced to contaminated water sources used in agricultural irrigation. Taco Bell stated it was cooperating fully with federal investigators and had taken swift action to remove the implicated product from its supply chain.