McDonald’s has reintroduced Quarter Pounders to its menus after the Colorado Department of Agriculture tested beef patties collected from locations across the state and found all samples to be negative for Escherichia coli. Overlaying the U.S. Centers for Disease Control and Prevention’s (CDC’s) epidemiological data with its supply chain traceback data, McDonald’s has ruled out beef patties as the source of the ongoing foodborne illness outbreak.

As of October 25, 2024, CDC has reported 75 illnesses, 22 hospitalizations, and one death in 13 U.S. West and Midwest states associated with the E. coli O157:H7 outbreak linked to McDonald’s Quarter Pounders. Not including the fatality, two patients developed Hemolytic Uremic Syndrome, at least one of whom—a 15-year-old girl in Colorado—is suffering kidney failure as a result.

Slivered onions sourced from a Taylor Farms facility in Colorado Springs, Colorado are the most likely cause of the outbreak, according to the U.S. Food and Drug Administration (FDA) and McDonald’s. The onions have been recalled by Taylor Farms.

The 900 McDonald’s restaurants that historically received slivered onions from Taylor Farms’ Colorado Springs facility will resume sales of Quarter Pounders without slivered onions. Those restaurants are located in Colorado, Kansas, and Wyoming, as well as portions of Idaho, Iowa, Missouri, Montana, Nebraska, Nevada, New Mexico, Oklahoma, and Utah. McDonald’s has also decided to stop sourcing onions from Taylor Farms’ Colorado Springs facility indefinitely.

McDonald’s is not the only foodservice chain to receive onions from Taylor Farms; therefore, brands like Taco Bell, Pizza Hut, and KFC have also pulled onions from their menus at certain locations.

FDA is continuing its investigation into Taylor Farms’ Colorado Springs facility.

Update, October 31, 2024: CDC has officially named Taylor Farms onions served at McDonald’s as the source of the outbreak, and has reported 90 illnesses, 27 hospitalizations, two cases of Hemolytic Uremic Syndrome, and one fatality.