McDonald's E. coli update: Contaminated onions came from California farm, officials say

CHICAGO - A deadly E. coli outbreak in the U.S. has been linked to McDonald’s Quarter Pounder hamburgers, and while federal investigators tried to pinpoint the exact cause, the fast food giant worked this week to reassure customers that its restaurants are safe. 

The U.S. Centers for Disease Control and Prevention said Tuesday that the outbreak had sickened at least 49 people in 10 states. One person died and 10 were hospitalized, according to the CDC.

Meanwhile, McDonald's pulled Quarter Pounders from 20% of its U.S. stores on Tuesday as a result. The company said it has worked closely with federal food safety regulators since late last week, when it was alerted to the potential outbreak. 

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 officials said the contaminated onions came from Taylor Farms, of Salinas, California.

U.S. Foods, a major wholesaler to restaurants across the country, said Thursday that Taylor Farms had issued a recall this week for peeled whole and diced yellow onions for potential E. coli contamination. The recalled onions came from a Taylor Farms facility in Colorado, a U.S. Foods spokesperson said. But the wholesaler also noted that it wasn't a McDonald's supplier and that its recall didn't include any products sold at the fast-food chain's restaurants.

Taylor Farms did not respond to multiple requests for comment, and the U.S. Food and Drug Administration would not confirm that the agency is investigating Taylor Farms. A spokesperson said told the Associated Press that the agency is "looking at all sources" of the outbreak.

Here’s what to know about the outbreak:

Which other fast-food restaurants have stopped using fresh onions? 

Other fast-food restaurants — including Taco Bell, Pizza Hut, KFC and Burger King — have temporarily pulled onions from some menus.

"As we continue to monitor the recently reported E. coli outbreak, and out of an abundance of caution, we have proactively removed fresh onions from select Taco Bell, Pizza Hut and KFC restaurants," Yum Brands said in a statement.

Louisville, Kentucky-based Yum Brands wouldn’t say where onions were removed or whether the company uses the same supplier as McDonald’s. Yum Brands said it will continue to follow guidance from regulators and its suppliers.

Restaurant Brands International, which owns Burger King, said Thursday that 5% of its restaurants use onions distributed by Taylor Farms’ Colorado facility. Burger King restaurants get deliveries of whole, fresh onions and its employees wash, peel and slice them.

Even though it wasn't contacted by health officials and it had no indications of illness, Restaurant Brands said it asked the restaurants that received onions from the Colorado facility to dispose of them two days ago. The company said it’s restocking with onions from other suppliers.

McDonald’s Quarter Pounder pulled off menu in these states

McDonald’s said its Quarter Pounders were removed from restaurant menus in the following states: 

• Colorado
• Kansas
• Utah
• Wyoming

Quarter Pounders have also been removed from menus in portions of:

• Idaho
• Iowa
• Missouri
• Montana
• Nebraska
• Nevada
• New Mexico
• Oklahoma

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 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 Quarter Pounder E. coli outbreak: What we know

The CDC reported the outbreak late on Tuesday. It said infections were reported between Sept. 27 and Oct. 11 in Colorado, Iowa, Kansas, Missouri, Montana, Nebraska, Oregon, Utah, Wisconsin and Wyoming.

State and local public health officials were interviewing people about the foods they ate in the week before they got sick. Of the 18 people interviewed as of Tuesday, all reported eating at McDonald’s, and 16 people reported eating a beef hamburger. Twelve reported eating a Quarter Pounder.

McDonald's said it's unlikely the beef in the Quarter Pounder was the source, since it comes from multiple suppliers and is cooked at a high enough temperature to kill E. coli.

The fast food company said its initial findings suggest that some of the reported illnesses were linked to onions from a single supplier, which the company didn't name. McDonald's said the onions are cleaned and sliced by the supplier and then packaged for use on individual Quarter Pounders.

McDonald's is known for its stringent food safety guidelines and protocols, Chris Gaulke, a professor of food and beverage management at Cornell University’s Nolan School of Hotel Administration, told the Associated Press. 

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 told the AP.

But some experts questioned why McDonald's simply stopped selling one sandwich and didn't close restaurants for further investigation.

"Good practice would have been to close all the restaurants," Bill Marler, a Seattle lawyer who has sued companies over food poisoning outbreaks, told the AP. "Until we know definitively what the product was that made people sick, consumers should be aware."

Marler said cross-contamination remains a potential possibility at the affected restaurants until they are thoroughly cleaned.

Asked why it didn't close any restaurants, McDonald’s said nothing in the government’s investigation indicated there were issues with its food preparation practices. In an interview on the "Today" show on Wednesday, McDonald's U.S. President Joe Erlinger also said it's likely that whatever product was contaminated has already passed through the company's supply chain.

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.

What is E. coli?

E. coli bacteria are found in many places, including in the environment, foods, water, and the intestines of people and animals, the CDC says. Infections can cause severe illness, including fever, stomach cramps and bloody diarrhea. 

Children under 5, adults 65 and up, people with weakened immune systems and international travelers are all at an increased risk for E. coli infection, the agency says.

Those who develop symptoms of E. coli poisoning should seek health care immediately and tell the provider what they ate.

The type of bacteria implicated in the McDonald's case causes about 74,000 infections in the U.S. annually, leading to more than 2,000 hospitalizations and 61 deaths each year, according to the CDC.