McDonald's deadly E. coli outbreak has now sickened more than 100 people

A deadly E. coli outbreak linked to slivered onions on McDonald's Quarter Pounder burgers has sickened 104 people in 14 states, federal health officials said in an update on Wednesday. 

At least 34 people have been hospitalized, and four developed hemolytic uremic syndrome (HUS), a serious condition that can cause kidney failure. An 88-year-old man who resided in Grand Junction, Colorado, died, as previously reported. The illnesses began at the end of September, and the most recent onset of illness occurred as of October 21, according to the U.S. Food and Drug Administration.

McDonald's in late October said its Quarter Pounders — without slivered onions — would return to the menus of hundreds of its impacted restaurants after testing ruled out beef patties as the source of the outbreak. 

The hamburger chain pulled the burgers from restaurants in several states after the outbreak was announced. 

The FDA and Colorado officials have collected onion and environmental samples from McDonald's stores and distribution centers. One sample of recalled onions tested positive for E. coli, but did not match the outbreak strain. 

Onion supplier Taylor Farms recalled yellow onions in the wake of the outbreak, and McDonald's has reintroduced slivered onions from a different supplier. 

"There does not appear to be a continued food safety concern related to this outbreak at McDonald's restaurants," the FDA stated.

It usually takes three to four weeks to determine if a sick person is part of an outbreak. Most people infected with the toxin-producing E. coli experience severe stomach cramps, diarrhea and vomiting. Most recover without treatment after five to seven days.

People are advised to call their health care provider if they ate a McDonald's Quarter Pounder and have severe E. coli symptoms.