TLDR:
- E. coli outbreak linked to McDonald’s affects 49 people across 10 states, with 1 death reported
- About 2,700 US McDonald’s locations (20%) have removed Quarter Pounders and onions
- McDonald’s stock dropped 5-7% following the outbreak news
- Onions from a single facility are suspected as the source rather than beef
- Company already facing challenges with declining same-store sales (first drop in 16 quarters)
McDonald’s Corporation faced significant market pressure Wednesday as its stock fell 5% following news of an E. coli outbreak linked to Quarter Pounder hamburgers, forcing the removal of the signature item from approximately 2,700 U.S. locations.
The Centers for Disease Control and Prevention (CDC) has confirmed 49 cases of E. coli infection across ten states, including Colorado, Iowa, Kansas, Missouri, Montana, Nebraska, Oregon, Utah, Wisconsin, and Wyoming. One death has been reported in Colorado, along with ten hospitalizations.
The fast-food giant learned of the outbreak late last week and quickly removed two ingredients from affected restaurants. The timeline of reported cases spans from September 27 to October 11, though the actual number of cases could be higher due to the CDC’s three-to-four-week verification process.

McDonald’s U.S. President Joe Erlinger appeared on the Today show to address public concerns, emphasizing the company’s immediate response to protect customer safety. “What is relevant today is that action has been made to shield the American public and advance its wellness,” Erlinger stated.
While the exact source remains under investigation, preliminary findings suggest onions may be the culprit rather than beef patties. Company spokespeople noted that the beef comes from multiple suppliers, making widespread contamination less likely. Additionally, McDonald’s safety protocols require burgers to be cooked at 175 degrees, well above the 160-degree temperature needed to kill E. coli.
All affected locations source their onions from a single facility, though a CDC spokesperson confirmed this would mark the first instance of onions being linked to E. coli. The agency continues to investigate both ingredients.
The outbreak comes at a challenging time for McDonald’s, which recently reported its first decline in U.S. same-store sales in 16 quarters. Second-quarter results showed a 0.7% decrease in same-store sales, driven by reduced foot traffic.
TD Cowen analyst Andrew Charles issued a note to clients suggesting it’s “likely premature to compare” this situation to Chipotle’s 2015-2018 E. coli outbreak, which resulted in a $25 million FDA fine. Charles estimates McDonald’s sales impact may last approximately one month.
Based on typical sales volumes, McDonald’s is estimated to have sold about 1 million Quarter Pounders in the affected geographic areas during the outbreak period.
The company’s stock performance has remained flat year-to-date, significantly underperforming compared to the S&P 500’s 22% increase during the same period.
McDonald’s plans to release its third-quarter results next Tuesday before the market opens. The company stated it’s too early to determine the outbreak’s impact on foot traffic and continues to work with health authorities to investigate the incident.
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