Quarter Pounders are off the menu at 20% of McDonald's in US as E. coli cases are investigated

McDonald’s worked Wednesday to reassure customers that its U.S. restaurants are safe as federal investigators tried to pinpoint the cause of a deadly E. coli outbreak linked to the fast-food giant's Quarter Pounder hamburgers.

McDonald's pulled Quarter Pounders from one-fifth of its U.S. stores Tuesday as a result of the outbreak, which the U.S. Centers for Disease Control and Prevention said had sickened at least 49 people in 10 states. One person died and 10 were hospitalized, according to the CDC.

A preliminary investigation by the U.S. Food and Drug Administration suggested fresh slivered onions that are served raw on Quarter Pounder hamburgers were a likely source of the contamination. McDonald's also serves raw, slivered onions on one of its breakfast sandwiches, but that sandwich isn't available at the impacted stores. Other burgers, like the Big Mac, use diced, cooked onions.

McDonald's said it was searching for a new regional supplier for fresh onions. In the meantime, Quarter Pounders were removed from menus in Colorado, Kansas, Utah, Wyoming, and portions of Idaho, Iowa, Missouri, Montana, Nebraska, Nevada, New Mexico, and Oklahoma.

Adriean Madden pulled up outside a McDonald’s outside Denver on Wednesday for his usual afternoon snack but then decided against it. He said he was unsure how E. coli spreads or contaminates other foods, and he thinks McDonald’s should be more forthcoming.

“This affects my decision with coming to McDonald’s in the future,” Madden said. “I feel like the information isn’t as widely spread. I didn’t see any notices on the door, and then I saw vehicles going through the drive through just as if nothing was going on.”

Colorado has had the most reported cases of any state so far, and it's where the one death involving an older adult occurred.

McDonald’s said it has worked closely with federal food safety regulators since late last week, when it was alerted to the potential outbreak. The company said the scope of the problem and the popularity of its products have complicated efforts to identify the contamination source.

McDonald's has more than 14,000 U.S. stores and serves 1 million Quarter Pounders every two weeks in the affected 12-state area.

McDonald's is known for its stringent food safety guidelines and protocols, said Chris Gaulke, a professor of food and beverage management at Cornell University’s Nolan School of Hotel Administration. The company said Wednesday that the supplier regularly tested its onions for E. coli, for example.

“Given the volume of food that they go through, how infrequently this happens to McDonald's is a testament to the effort that they take,” Gaulke said.