The Centers for Disease Control and Prevention (CDC) has confirmed that a fast-moving E. coli O157:H7 outbreak has been linked to McDonald’s Quarter Pounder hamburgers, with the onions used on the burgers emerging as the prime suspect. This outbreak, which spans ten states, has prompted McDonald’s to pull certain ingredients and temporarily halt the sale of Quarter Pounders in several regions. 

Public health officials from the CDC, the U.S. Food and Drug Administration (FDA), and the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS) are working with state agencies to trace the source of the contamination. The outbreak has affected states including Oregon, Montana, Wyoming, Colorado, and Kansas, but so far, no cases have been reported in southern states like Tennessee. 

As of October 22, 49 cases of E. coli infection have been confirmed, with illness onset dates ranging from September 27 to October 11, 2024. Among those infected, 10 people have been hospitalized, and one person has developed hemolytic uremic syndrome (HUS), a severe condition that can cause kidney failure. Tragically, one death has been reported—an older adult in Colorado. 

The CDC reports that all 18 patients interviewed so far had eaten at McDonald’s, with 86% specifically identifying a Quarter Pounder as their meal. While many individuals fell ill shortly after dining at McDonald’s in their home states, at least one patient reported eating at a McDonald’s location while traveling. 

To safeguard customers, McDonald’s has temporarily ceased using fresh slivered onions and beef patties used in Quarter Pounders across several states. The company has assured customers that Quarter Pounders will not return to menus until the investigation is complete and the risk is mitigated. 

The true extent of the outbreak may be greater than current numbers reflect, as many people recover without seeking medical attention and may go untested for E. coli. Public health officials emphasize that identifying the full scope of the outbreak can take several weeks due to reporting delays. 

Anyone who has recently eaten a Quarter Pounder from McDonald’s and experiences symptoms of severe E. coli infection—such as abdominal cramps, diarrhea, or vomiting—is urged to seek medical attention promptly.