The FDA, CDC, USDA-FSIS, and various state and local public health agencies are working to track and contain a fast-moving outbreak of E. coli O157:H7 illnesses that has sickened forty-nine individuals in ten states.
Epidemiological data based on interviews of eighteen patients revealed all eighteen of the interviewees ate at a McDonald’s in the week before falling ill. Sixteen of the eighteen remembered having consumed a beef hamburger. Of the sixteen, twelve reported eating a Quarter Pounder.
The first victim became ill on September 27, 2024; the most recent victim developed symptoms on October 11th. Ten of the forty-nine confirmed outbreak victims have been hospitalized, including one who has developed hemolytic uremic syndrome (HUS).
One person—an older adult from Colorado who did not develop HUS— has died.
Outbreak victims have been reported in Colorado (26), Iowa (1), Kansas (1), Missouri (1), Montana (1), Nebraska (9), Oregon (1), Utah (4), Wisconsin (1), and Wyoming (4).
Victims range in age from 13 to 88 years of age, with a median age of 26. Nearly two-thirds (63%) of the victims are male.
The source
Although the specific ingredient behind the contaminated Quarter Pounders has not yet been identified, FDA and USDA-FSIS appear to be focused on either the slivered onions or the beef patties. McDonald’s stores in Colorado, Kansas, Utah, Wyoming, and portions of Idaho, Iowa, Missouri, Montana, Nebraska, Nevada, New Mexico, and Oklahoma have temporarily stopped using Quarter Pounder slivered onions and beef patties.
The FDA is investigating the slivered onions, while the USDA-FSIS is concentrating on tracing back hamburger patties served at McDonald’s in affected states.
McDonald’s statement
McDonald’s has issued the following statement:
Across the McDonald’s System, serving customers safely in every single restaurant, each and every day, is our top priority and something we’ll never compromise on.
It is why we are taking swift and decisive action following an E. Coli outbreak in certain states. 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.
Out of an abundance of caution, we are also temporarily removing the Quarter Pounder from restaurants in the impacted area, including Colorado, Kansas, Utah and Wyoming, as well as portions of Idaho, Iowa, Missouri, Montana, Nebraska, Nevada, New Mexico, and Oklahoma. We take food safety extremely seriously and it’s the right thing to do. Impacted restaurants are receiving a stock recovery notice today and should reach out to their field supply chain manager or distribution center with any questions.
We are working in close partnership with our suppliers to replenish supply for the Quarter Pounder in the coming weeks (timing will vary by local market). In the meantime, all other menu items, including other beef products (including the Cheeseburger, Hamburger, Big Mac, McDouble and the Double Cheeseburger) are unaffected and available. We will continue to work with the Centers for Disease Control and Prevention (CDC) and are committed to providing timely updates as we restore our full menu.“
What consumers need to know (CDC)
McDonald’s has stopped using fresh slivered onions and quarter pound beef patties in several states to protect their customers while a source of illness is confirmed.
Call your healthcare provider if you ate a McDonald’s Quarter Pounder hamburger and have severe E. coli symptoms:
- Diarrhea and a fever higher than 102°F
- Diarrhea for more than 3 days that is not improving
- Bloody diarrhea
- So much vomiting that you cannot keep liquids down
- Signs of dehydration, such as:
- Not peeing much
- Dry mouth and throat
- Feeling dizzy when standing up
Symptoms of E. coli O157:H7
- Most people infected with Shiga toxin-producing E. coli experience severe stomach cramps, diarrhea (often bloody), and vomiting.
- Symptoms usually start 3 to 4 days after swallowing the bacteria.
- Most people recover without treatment after 5 to 7 days.
- Some people may develop serious kidney problems (hemolytic uremic syndrome, also called HUS) and would need to be hospitalized
- For more information about E. coli, see the CDC’s E. coli Questions and Answers page.

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