A person has died due to the consumption of a McDonald’s Quarter Pounder sandwich contaminated with Escherichia coli, reported the U.S. Centers for Disease Control and Prevention (CDC) on October 23. In addition to the fatality, there have been 49 cases of illness and ten hospitalizations linked to this foodborne illness outbreak across ten states, since the investigation was opened on October 22, 2024.

CDC, the U.S. Food and Drug Administration (FDA), the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS), and multiple state public health departments are looking into the ongoing foodborne illness outbreak of E. coli O157:H7 infections. The majority of case patients reported eating a McDonald’s Quarter Pounder prior to the onset of illness. Most illnesses have been reported in Colorado and Nebraska, and eight other states have also been implicated in the outbreak (Iowa, Kansas, Missouri, Montana, Oregon, Utah, Wisconsin, and Wyoming).

Although a specific ingredient has not yet been confirmed as the source of the outbreak, preliminary traceback and distribution information reviewed by FDA points to slivered onions (not including diced onions) served on the Quarter Pounders as the most probable vehicle of illness. The slivered onions used in the Quarter Pounders are sourced from a single supplier that serves three distribution centers.

An official recall has not been announced by FDA, but McDonald’s has temporarily stopped using slivered onions in the states that receive slivered onions from the implicated supplier. Additionally, McDonald’s has temporarily removed the Quarter Pounder from its menu in Colorado, Kansas, Utah, and Wyoming, as well as parts of Idaho, Iowa, Missouri, Montana, Nebraska, Nevada, New Mexico, and Oklahoma.

To rule out ground beef as a source of the illnesses, USDA-FSIS is conducting traceback on hamburger patties served at McDonald’s in affected states.

Update, October 25, 2024: FDA has reported that 75 people have been infected with the outbreak strain of E. coli O157:H7 across 13 states. Of 61 people with information available, 22 have been hospitalized, two people developed hemolytic uremic syndrome (HUS), and one death has been reported from an older adult in Colorado (not one of the HUS patients). Of the 42 people interviewed, 100 percent report eating at McDonald’s, and 39 people report eating a beef hamburger. New states in which cases have been reported include Michigan, New Mexico, and Wisconsin.

FDA has confirmed Taylor Farms as the supplier of the slivered onions for the affected McDonald's locations, and has initiated a voluntary recall. FDA is still working to confirm that the onions are the source of the outbreak.

Update, October 29, 2024: The Colorado Department of Agriculture reported that burger patties from McDonald's Quarter Pounders have tested negative for E. coli. McDonald's has reintroduced Quarter Pounders to its menus.

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.