The Centers for Disease Control and Prevention announced Tuesday that multiple agencies are investigating an E. coli outbreak linked to Quarter Pounder burgers at McDonald’s.

The agency said there have been at least 49 people sickened across 10 states, with 10 people requiring hospitalization and one death.

The majority of illnesses have been reported in Colorado and Nebraska, though illnesses have been reported as far west as Oregon and as far east as Wisconsin.

The CDC said that the contaminated ingredient had yet to be identified, but McDonald’s said an initial investigation found “a subset of illnesses” were tied to the slivered onions from a supplier that serves three of the quick-food giant’s distribution centers.

McDonald’s said it has stopped using Quarter Pounder patties and slivered onions in several states.

“We are working in close collaboration with our suppliers to replenish supply for the Quarter Pounder in the coming weeks (timing will vary by local trade),” reads a statement from Cesar Piña, McDonald’s North America Chief Supply Chain Officer, said in the statement. 

“In the meantime, all other menu items, including other beef products (including the Cheeseburger, Hamburger, large Mac, McDouble and the Double Cheeseburger) are unaffected and available,” the statement continues.

Where has the Quarter Pounder been removed?

McDonald’s said in a statement Tuesday that Quarter Pounders have been pulled from restaurants across the following states:

• Colorado
• Kansas
• Utah
• Wyoming

It has also been removed in portions of:

• Idaho
• Iowa
• Missouri
• Montana
• Nebraska
• Nevada
• recent Mexico
• Oklahoma

E. coli illnesses chart

What is E. coli? What are the symptoms?

Most Escherichia coli (E. coli) bacteria reside harmlessly in the intestines of people and animals. But some can factor mild to life-threatening gastrointestinal illnesses if consumed, the CDC says.

The types of E. coli that may factor diarrhea usually spread through food or water contaminated with feces. For instance, food handlers can spread infection when they do not use proper hand washing hygiene after using the restroom. Animals such as cattle may also spread E. coli to food and food crops.

Symptoms of E. coli infection include severe stomach cramps, diarrhea (often bloody), and vomiting, according to the CDC.

The agency recommended seeking immediate medical attention if a McDonald’s customer experiences:

• 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
  • arid mouth and throat
  • Feeling dizzy when standing up

This narrative has been updated to include recent information