CHICAGO – McDonald’s said Wednesday that customers should feel confident ordering from its restaurants despite a deadly E. coli outbreak linked to its Quarter Pounders.

McDonald’s U.S. President Joe Erlinger said in an interview on the “Today” show that the company has removed the Quarter Pounder from its menu in the 10 states where dozens of people were sickened, as well as in several other states.

A preliminary investigation by the U.S. Food and Drug Administration suggests raw onions served on Quarter Pounders are a likely source of contamination, and McDonald’s said its initial findings suggest that some of the reported illnesses are linked to onions from a single supplier. The U.S. Department of Agriculture is investigating the hamburger meat.

McDonald’s Takes Action to Protect Public Health

“What’s important today is that we’ve taken the action to protect the American public and promote public health,” Erlinger said. “We’re confident that we’ll see our way through this and will restore confidence for the American consumer to come to McDonald’s.”

The U.S. Centers for Disease Control and Prevention reported the outbreak late Tuesday. It said 49 infections were reported between Sept. 27 and Oct. 11 in Colorado, Iowa, Kansas, Missouri, Montana, Nebraska, Oregon, Utah, Wisconsin and Wyoming. One person in Colorado died and 10 people were hospitalized. All of them mentioned eating Quarter Pounders, which contain a beef burger topped with pickles, slivered onions and a sesame seed bun.

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Experts Weigh in on E. Coli Incubation Period

The incubation period for E. coli is only a couple of days, so illness would be quickly apparent to anyone affected, said Donald Schaffner, a food safety expert at Rutgers University. “If you ate these burgers in September and now it’s the middle of October and you didn’t get sick, you’re probably OK,” he said.

E. coli bacteria are harbored in the guts of animals and found in the environment. Infections can cause severe illness, including fever, stomach cramps and bloody diarrhea. People who develop symptoms of E. coli poisoning should seek health care immediately and tell the provider what they ate.

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McDonald’s Cooperates With Investigation

Erlinger said it’s possible the contaminated product has already worked its way through McDonald’s supply chain. But the company will work closely with the government and cooperate with the investigation, he said. Erlinger declined to name the supplier or say if it supplies other restaurant chains or grocery stores.

McDonald’s shares fell 4.5% in early trading Wednesday.