McDonald’s E. Coli Outbreak Declared Over

Federal health agencies closed their investigations into the bacterial outbreak that sickened 104 people and was linked to onions on the fast-food chain’s signature Quarter Pounders.

Health officials have closed their investigations into an E. coli outbreak linked to raw onions on McDonald’s Quarter Pounder hamburgers that sickened more than a hundred people, the Food and Drug Administration announced Tuesday.

In total, 104 people from 14 states were sickened from the contaminated food and 34 were hospitalized. One older person in Colorado died.

Officials said there did not appear to be a “continued food safety concern,” because McDonald’s had not served slivered onions — which investigators determined to be the “likely source of contamination”— on the Quarter Pounders for more than a month. The onions were recalled. And in many states, Quarter Pounders were removed from the menu altogether for several weeks.

There have not been any new illnesses since McDonald’s decided to remove the onions from its menu on Oct. 22, according to the Centers for Disease Control and Prevention.

Evidence linking the onions to the food-borne illnesses was limited. According to the F.D.A., one sample from the recalled onions supplied by Taylor Farms, a large vegetable and fruit grower, and an environmental sample from an onion grower in Washington State tested positive for E. coli. But those samples did not match the bacterial strain found in those customers who became ill, the agency said.

Still, the F.D.A. investigation determined that the yellow onions were the likely source of the outbreak based on interviews with those who were sickened and from information provided by the distributors of the product. Of the people who recalled what they ate, roughly 84 percent had a menu item with slivered onions.