As health officials hunt cause of E. coli cases at McDonald's, fast food chains and suppliers hold the onions

Food companies and restaurant chains stopped using onions Thursday as authorities tried to pinpoint the source of a potentially fatal E. coli outbreak among people who ate McDonald’s Quarter Pounder hamburgers.

Public health officials said slivered onions on Quarter Pounders consumed mostly in Mountain West states are a possible cause of the infections. Most of the 49 listed cases come from Colorado, where one victim died.

While no cases have been uncovered in Illinois, agencies found one illness in Iowa and another in Wisconsin. Suppliers of onions and other ingredients can serve many end users, so there are concerns that E. coli cases could spread beyond McDonald’s.

Taylor Farms, based in Salinas, California, provided the slivered onions on Quarter Pounders involved in the spread of E. coli, Chicago-based McDonald’s said.

In its public statements, McDonald’s assured customers of its commitment to food safety. Working closely with regulators, it also said its other beef products, such as the cheeseburger and Big Mac, are unaffected.

“The initial findings from the investigation indicate that a subset of illnesses may be linked to slivered onions used in the Quarter Pounder and sourced by a single supplier that serves three distribution centers,” McDonald’s chief supply chain officer for North America Cesar Pina said.

By pulling Quarter Pounders from menus in all or parts of 12 states, McDonald's has removed the popular burgers from about one-fifth of its U.S. restaurants.

Its fast food competitors such as Taco Bell, Pizza Hut, KFC and Burger King said they pulled onions from some menus as a precaution.

Rosemont-based US Foods Holding, a large supplier to restaurants and food service operators, said it was asking customers not to use onions supplied by Taylor Farms Colorado.

US Foods spokeswoman Sara Matheu said the company responded to Taylor Farms’ own recall of its onion products. “We take food safety very seriously, and as aligned with our rigorous recall process, we are contacting impacted US Foods customers with appropriate recall instructions,” she said.

Matheu did not say how many of its customers are affected by the recall. US Foods is not a McDonald’s supplier.

CNBC reported that the Food and Drug Administration is investigating Taylor Farms as a source of the outbreak, but the agency declined to confirm that in a statement to the Sun-Times, saying only that it “is still looking at all possible sources.”

Taylor Farms did not answer requests for comment. The company has a deli division at 200 N. Artesian Ave., near West Fulton Street and North Western Avenue. It’s not known if the deli unit has any part in the onion recall.

The FDA and the U.S. Centers for Disease Control and Prevention also are examining the fresh beef patties used in Quarter Pounders. McDonald’s has said the patties are unlikely to blame because they are cooked at high enough temperatures to kill E. coli.

“This is a fast-moving outbreak investigation,” the CDC said.

Word of the infections caused some investors to dump McDonald’s stock on concerns that people will avoid its food. The shares, part of the Dow Jones Industrial Average, lost more than 5% of their value Wednesday but recovered somewhat Thursday as analysts speculated the effect on the company will pass quickly.

Morningstar analyst Sean Dunlop called the market’s reaction “slightly overstated, leaving shares trading in a range we consider fairly priced.” McDonald’s stock rose about 1% Thursday to close at $301.58 a share.

“Food safety issues are a key environmental, social, and governance risk for restaurateurs, given that their brand strength rests heavily on consumer trust. That said, considering larger brands' sprawling store footprints and diverse supplier bases, small outbreaks happen every couple of years,” Dunlop wrote in an online note. “Consumers tend to be most forgiving when management is transparent, takes quick remedial action, can definitively source the issue, and avoids repeating mistakes.”

Meanwhile, the first lawsuit against McDonald’s over E. coli was filed Wednesday in Cook County Circuit Court. Eric Stelly, a resident of Greeley, Colorado, is suing for damages because he was diagnosed with an E. coli illness Oct. 6, two days after eating at McDonald’s.

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. Death occurs in limited cases. The CDC said the infections probably are more common than reported because many people do not seek treatment.

Of the 49 victims who ate at McDonald’s, 10 have been hospitalized, the CDC said.

Contributing: AP