Full List & Map Of States Affected By McDonald's E. Coli Outbreak

An E. coli outbreak linked to McDonald's Quarter Pounder burgers in the U.S. has sickened at least 49 people and caused one death. Cases have been reported in 10 states so far, with the most illnesses in Colorado and Nebraska.

On Tuesday, the U.S. Centers for Disease Control and Prevention posted a food safety alert announcing it was investigating a multi-state outbreak of E. coli O157:H7 infections linked to contaminated McDonald's Quarter Pounders.

The CDC called the outbreak "severe" in a press release, adding that McDonald's has temporarily removed the suspected ingredients.

Escherichia coli (E. coli) is bacteria found in the intestines of humans and animals. Some types, like E. coli O157:H7, can produce powerful toxins that can cause severe and potentially deadly illness. Symptoms include bloody diarrhea, vomiting and a fever.

In this outbreak, at least 49 cases of E. coli have been reported in 10 states so far, but "the true number of sick people is likely much higher," the CDC said.

Everyone interviewed as part of the investigation reported eating a McDonald's hamburger before developing symptoms, with most specifically mentioning Quarter Pounders.

In a statement released on Oct. 22, McDonald's said it was taking “taking swift and decisive action.”

Quarter Pounders are temporarily unavailable for purchase at McDonald’s stores in 11 states, per the CDC, and investigators are working to determine which specific ingredient or ingredients are contaminated with E. coli.

Two ingredients used in Quarter Pounders are currently being investigated: fresh slivered onions and quarter-pound beef patties, the CDC said.

Joining TODAY on Oct. 23, McDonald's USA President Joe Erlinger addressed the outbreak, stating that consumers can "confidently go to McDonald’s today" and eat the classics without getting sick.

“Food safety is our top priority at McDonald’s," Erlinger said.

There has been one death of an older adult in Colorado due to the outbreak. At least 10 people have been hospitalized, including one child who has developed hemolytic uremic syndrome (HUS), a serious condition that can lead to kidney failure, the CDC said.

The people sickened range in age from 13 to 88.

The illnesses linked to this outbreak started between Sept. 27, 2024 and Oct. 11, 2024. It's also possible that there are more recent illnesses that have yet to be reported, since it can take three to four weeks to link an individual's sickness to an outbreak, per the CDC.

The outbreak has affected 10 states so far, with Colorado reporting the highest number of cases, followed by Nebraska and Wisconsin, according to the latest data from the CDC.

"This outbreak may not be limited to the states with known illnesses, and the true number of sick people is likely much higher than the number reported," the CDC said on its website.

If you have questions about specific cases in your state, contact your state's department of health, the CDC advised in a press release.

As the outbreak investigation continues, McDonalds stores in multiple states have temporarily stopped selling Quarter Pounder beef patties and fresh slivered onions.

The quarter-pound patties are only used on Quarter Pounders, and the slivered onions are "primarily used on Quarter Pounders and not other menu items," the CDC said.

McDonald’s stores in the following states (or portions of states) have temporarily removed Quarter Pounders from their menus:

Portions of:

E. coli is a type of bacteria found in the environment, food, water, and in the digestive tract of humans and animals, per the CDC. While most types of E. coli are harmless, some types can cause disease.

Certain strains, such as E. coli O157:H7, can produce powerful Shiga toxins that can cause life-threatening illness. The most common such strain in the U.S. is E. coli O157:H7, which is involved in the McDonald's Quarter Pounder outbreak.

Symptoms of infection with E. coli O157:H7 include:

Symptoms usually start three to four days after ingesting the bacteria or contaminated food, per the CDC.

Most people will recover within a week, but some people can develop dehydration or life-threatening complications, including hemolytic uremic syndrome, which can lead to kidney failure.

The CDC urges anyone who has eaten a Quarter Pounder from McDonald's recently and experienced severe symptoms to call their healthcare provider.

If you experience signs of dehydration (decreased urination, dry mouth, dizziness), severe vomiting, or a fever over 102 degrees Fahrenheit, seek immediate medical attention and tell the health care provider what you ate.

Caroline Kee

Caroline Kee is a health reporter at TODAY based in New York City.