McDonald’s E. coli Outbreak – was it the beef or the onions?

CDC, public health and regulatory officials in several states, the U.S. Food and Drug Administration (FDA), and the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS) are collecting different types of data to investigate a multistate outbreak of E. coli O157:H7 infections.

Epidemiologic data show that Quarter Pounder hamburgers served at McDonald’s are contaminated with E. coli and are making people sick. Early information from FDA indicates onions may be a source of this outbreak. Investigators from all agencies are working quickly to determine the contaminated ingredient.

As of October 22, 49 people infected with the outbreak strain of E. coli O157:H7 have been reported from 10 states. Illnesses started on dates ranging from Sept 27, 2024, to October 11, 2024. Of 28 people with information available, 10 have been hospitalized, and 1 person developed hemolytic uremic syndrome, a serious condition that can cause kidney failure. One death has been reported from an older adult in Colorado. This is not the same person with HUS.

State and local public health officials are interviewing people about the foods they ate in the week before they got sick. Of the 18 people interviewed, all 18 (100%) report eating at McDonald’s, and 16 people report eating a beef hamburger. Of 14 people who remember the specific beef hamburger they ate at McDonald’s, 12 (86%) report eating a Quarter Pounder hamburger. Some people in this outbreak reported traveling to other states before their illness started. At least one person ate at McDonald’s during their travel. Investigators are working to determine if the slivered onions or beef patties in Quarter Pounder burgers are the specific source of this outbreak.

Preliminary traceback and distribution information reviewed by FDA shows that slivered onions served on Quarter Pounders are a likely source of contamination. FDA is working quickly to confirm that these onions are a source of this outbreak and to determine if these onions were served or sold at other businesses.

FSIS is conducting traceback on hamburger patties served at McDonald’s to determine if ground beef is a source of illness.

McDonalds has stopped using fresh slivered onions and quarter pound beef patties in several states to protect their customers while a source of illness is confirmed. Quarter Pounders will not be available for sale temporarily in some states. Call your healthcare provider if you ate a McDonald’s Quarter Pounder hamburger and have severe E. coli symptoms.

Republished with permission from Bill Marler and Marler Clark. Copyright (c) Marler Clark LLP, PS. All rights reserved.