So far in 2025, a Listeria outbreak linked to frozen nutritional shakes served at long-term care facilities and nursing homes has dominated the news. Several outbreaks in 2024 also made headlines including a Listeria outbreak linked to Boar’s Head deli meats and an E. coli outbreak connected to contaminated slivered onions at internationally famous fast food chain McDonald’s.
McDonald’s E. coli Outbreak Background
In October 2024, a multistate E. coli O157:H7 outbreak linked to McDonald’s Quarter Pounder burgers sickened 104 people across 14 states, resulting in 34 hospitalizations, and one death. According to a McDonald’s E. coli lawsuit attorney Tony Coveny, PhD.: “By nearly any account, this is likely a small sample of the number of patrons who really got sick. According to the CDC, only about 1 in 30 victims is actually identified in many outbreaks.”
The outbreak, which spanned September 27 to October 21, 2024, forced McDonald’s to take precautionary measures and temporarily suspend the use of two ingredients in affected regions: fresh slivered onions and quarter-pound beef patties. The quarter-pound beef patties were only used in McDonald’s Quarter Pounder hamburgers, while the fresh slivered onions primarily appeared in this menu item and rarely in other offerings.
While lab tests on onions detected E. coli strains, none matched the outbreak strain. This is not uncommon, however, as tainted (or adulterated) products are very often off the shelf or out of circulation (replaced by new product) by the time an outbreak is identified. But even without a positive sample (a “smoking gun if you will), investigations by federal, state, and local health agencies were able to conclusively identify fresh slivered onions supplied by Taylor Farms’ Colorado Springs facility as the likely source of contamination. According to Coveny, “no real doubt exists as to the source of the outbreak.”
What is E. coli and Why is it Dangerous?
This outbreak was particularly concerning due to its rapid spread across multiple states and the severity of cases, including one death. E. coli O157:H7 is a particularly dangerous strain of bacteria that can cause severe illness, especially in vulnerable populations such as the elderly, young children, and those with compromised immune systems.
The majority of E. coli strains are not harmful and play a crucial role in maintaining a healthy gut ecosystem by assisting in breaking down the food, contributing to the production of essential vitamins, and acting as a defense mechanism against more dangerous microorganisms.
However, not all E. coli are benign. Certain strains can cause a range of health issues in humans, including gastrointestinal distress resulting in diarrhea, infections of the urinary tract, respiratory ailments like pneumonia, systemic infections such as sepsis, and hemolytic uremic syndrome (HUS) – a potentially deadly complication that can severely damage the kidneys and other vital organs. Those infected with E. coli usually exhibit symptoms within 3 to 4 days after ingesting the bacteria.
Legal Impact
Unsurprisingly, the outbreak and resulting illnesses triggered multiple lawsuits against McDonald’s and Taylor Farms. Among the first was a lawsuit filed by E. coli lawfirm Ron Simon & Associates on behalf of Eric Stelly, a Colorado resident who developed severe symptoms after eating a contaminated burger, alleging negligence and breach of warranty.
By late October 2024, over three dozen plaintiffs, including cases of hemolytic uremic syndrome (HUS), were represented by Ron Simon & Associates, signaling potential long-term legal and financial repercussions for both companies. Many of these claims and lawsuits remain ongoing, though a significant number are believed to have settled, the terms of which are subject to confidentiality agreements.
Business Impact
The outbreak significantly dented McDonald’s customer traffic, with visits dropping 10% nationwide and 33% in Colorado shortly after the announcement. Sales of Quarter Pounders, a flagship product, stalled in 900 restaurants until an alternative onion supplier was secured. To regain trust, McDonald’s emphasized transparency, reinstated menu items by late October, and launched promotions like $5 value meals. Despite these efforts, McDonald’s Q4 2024 performance saw a 1.4% decline in U.S. same-store sales, the company’s weakest quarterly showing since the second quarter of 2020, near the start of the COVID-19 pandemic.
Against these challenges, U.S. franchisee performance ultimately demonstrated resilience, with locations averaging cash flows exceeding $500,000 per unit in 2024. The company notably maintained its strongest share of lowest-income consumers during the fourth quarter, contrasting sharply with broader industry declines in this demographic segment.
For 2025, the company planned to continue expanding with another 2,200 restaurants globally. By the end of 2024, McDonald’s counted over 43,000 locations worldwide with ambitious plans to achieve 50,000 stores by 2027.
It remains to be seen if ongoing litigation adn publicity impact McDonald’s sales in the coming months and years.
