WEDNESDAY, Oct. 23, 2024 (HealthDay News) -- An E. coli outbreak tied to McDonald's Quarter Pounders has sickened 49 people in 10 states, killing one and landing 10 more in the hospital.

Most of the illnesses have been reported in Colorado and Nebraska, and one child developed a serious complication known as hemolytic uremic syndrome, according to the U.S. Centers for Disease Control and Prevention.

"This is a fast-moving outbreak investigation," the agency said in a food safety alert issued Monday. "Most sick people are reporting eating Quarter Pounder hamburgers from McDonald’s and investigators are working quickly to confirm which food ingredient is contaminated. McDonald’s has pulled ingredients for these burgers, and they won’t be available for sale in some states."

The CDC also noted that information reviewed by the U.S. Food and Drug Administration suggests slivered onions may be the source of contamination.

In the meantime, McDonald’s has stopped using the onions, as well as quarter-pound beef patties, in several states while the investigation continues, the CDC added.

In a statement, McDonald's said initial findings have linked the onions to “a single supplier that serves three distribution centers.”

“We are working in close partnership with our suppliers to replenish supply for the Quarter Pounder in the coming weeks [timing will vary by local market],” the company said. “In the meantime, all other menu items, including other beef products [including the Cheeseburger, Hamburger, Big Mac, McDouble and the Double Cheeseburger] are unaffected and available.”

According to the FDA, McDonald’s has removed the slivered onions and quarter-pound patties from stores in Colorado, Kansas, Utah, Wyoming and portions of Idaho, Iowa, Missouri, Montana, Nebraska, Nevada, New Mexico and Oklahoma. In other states, Quarter Pounder burgers may not be available.

The FDA added that it "is working quickly to confirm that these onions are a source of this outbreak and to determine if these onions were served or sold at other businesses. McDonald’s has temporarily stopped using this type of onion in these states. Diced onions used at McDonald’s are not implicated in this outbreak."

However, the CDC noted the outbreak could eventually extend beyond the affected states.

E. coli infections include symptoms such as severe stomach cramps, diarrhea, fever and vomiting, which typically begin three or four days after exposure. Although most people recover without treatment within a week, others can develop serious kidney problems and require hospitalization, according to the CDC.

Anyone who becomes ill after eating a McDonald’s Quarter Pounder should get medical attention and tell the provider what they ate, the CDC stressed.

More information

The CDC has more on E. coli.

SOURCES: U.S. Centers for Disease Control and Prevention, news release, Oct. 22, 2024; U.S. Food and Drug Administration, safety alert, Oct. 22, 2024; McDonald's, statement, Oct. 22, 2024