CDC investigating E. Coli outbreak tied to US McDonald's Quarter Pounders

ATLANTA, GA - The Centers for Disease Control and Prevention is investigating a fast-moving outbreak of E. coli O157 infections linked to McDonald's Quarter Pounder hamburgers.

The outbreak has affected 49 people across 10 states, resulting in 10 hospitalizations and one death.

The CDC reports Tuesday that the majority of those infected had consumed McDonald's Quarter Pounders before falling ill.

While it is not yet clear which specific ingredient is responsible, the fast-food chain has taken precautionary measures, temporarily halting the use of fresh slivered onions and quarter pound beef patties in several states as investigators work to identify the source of the contamination.

Affected regions and precautionary actions

The outbreak has hit states such as Colorado and Nebraska particularly hard. 

McDonald’s has pulled affected ingredients to prevent further spread of illness, causing Quarter Pounders to be temporarily unavailable in certain areas. The company is cooperating with the CDC, FDA, USDA and state health officials to trace the contamination source and determine if it affects other restaurants or retailers.

Symptoms and recommendations

According to the CDC, E. coli infection symptoms can include severe stomach cramps, diarrhea (often bloody) and vomiting, typically appearing 3 to 4 days after exposure. The CDC urges anyone who has eaten a McDonald’s Quarter Pounder and is experiencing severe symptoms — like high fever, persistent diarrhea or dehydration — to contact their healthcare provider immediately.

In severe cases, E. coli can lead to a serious kidney condition known as hemolytic uremic syndrome, which may require hospitalization.

What is McDonald's doing?

McDonald’s has stopped the use of fresh slivered onions and quarter pound beef patties while the investigation is ongoing. The company is taking a proactive stance to protect its customers, stating that fresh slivered onions are primarily used on Quarter Pounders and not on other menu items, reducing the risk of broader contamination.

For more information on E. coli, symptoms, and outbreak updates, visit the CDC’s E. coli questions and answers page.

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