The initial findings from the investigation indicate that a subset of illnesses may be linked to slivered onions used in the Quarter Pounder and sourced by a single supplier that serves three distribution centers. As a result, and in line with our safety protocols, all local restaurants have been instructed to remove this product from their supply and we have paused the distribution of all slivered onions in the impacted area.
As of October 22, 49 people infected with the outbreak strain of E. coli O157:H7 have been reported from 10 states – Oregon, Montana, Wyoming, Utah, Colorado, Nebraska, Kansas, Iowa, Missouri and Wisconsin. Illnesses started on dates ranging from Sept 27, 2024, to October 11, 2024. Of 28 people with information available, 10 have been hospitalized, and 1 person developed hemolytic uremic syndrome, a serious condition that can cause kidney failure. One death has been reported from an older adult in Colorado.

CDC, public health and regulatory officials in several states, the U.S. Food and Drug Administration (FDA), and the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS) are collecting different types of data to investigate a multistate outbreak of E. coli O157:H7 infections.
Epidemiologic data show that Quarter Pounder hamburgers served at McDonald’s are contaminated with E. coli and are making people sick. Early information from FDA indicates onions may be a source of this outbreak. Investigators from all agencies are working quickly to determine the contaminated ingredient.
Preliminary traceback and distribution information reviewed by FDA shows that slivered onions served on Quarter Pounders are a likely source of contamination. FDA is working quickly to confirm that these onions are a source of this outbreak and to determine if these onions were served or sold at other businesses. FSIS is conducting traceback on hamburger patties served at McDonald’s to determine if ground beef is a source of illness.
William “Bill” Marler has been a food safety lawyer and advocate since the 1993 Jack-in-the-Box E. coli Outbreak which was chronicled in the book, “Poisoned” and in the recent Emmy Award winning Netflix documentary by the same name. Bill work has been profiled in the New Yorker, “A Bug in the System;” the Seattle Times, “30 years after the deadly E. coli outbreak, A Seattle attorney still fights for food safety;” the Washington Post, “He helped make burgers safer, Now he is fighting food poisoning again;” and several others.
Dozens of times a year Bill speaks to industry and government throughout the United States, Canada, Europe, Africa, China and Australia on why it is important to prevent foodborne illnesses. He is also a frequent commentator on food litigation and food safety on Marler Blog. Bill is also the publisher of Food Safety News.
E. coli: Marler Clark, The Food Safety Law Firm, is the nation’s leading law firm representing victims of E. coli outbreaks and hemolytic uremic syndrome (HUS). The E. coli lawyers of Marler Clark have represented thousands of victims of E. coli and other foodborne illness infections and have recovered over $900 million for clients. Marler Clark is the only law firm in the nation with a practice focused exclusively on foodborne illness litigation. Our E. coli lawyers have litigated E. coli and HUS cases stemming from outbreaks traced to ground beef, raw milk, lettuce, spinach, sprouts, and other food products. The law firm has brought E. coli lawsuits against such companies as Jack in the Box, Dole, ConAgra, Cargill, and Jimmy John’s. We have proudly represented such victims as Brianne Kiner, Stephanie Smith and Linda Rivera.
If you or a family member became ill with an E. coli infection or HUS after consuming food and you’re interested in pursuing a legal claim, contact the Marler Clark E. coli attorneys for a free case evaluation.
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