Start date of the investigation: October 22, 2024

Investigation status: Open

Callback issued: NO

This is a rapidly moving outbreak investigation. Most of those sickened report eating Quarter Pounder hamburgers from McDonald's, and investigators are working quickly to determine which food ingredient is contaminated. McDonald's has withdrawn the ingredients for these burgers and they are not available for sale in some states.

United States

  • cases: 49
  • Hospital stays: 10
  • Deaths: 1
  • States: 10

This is a rapidly moving outbreak investigation. Most of those sickened report eating Quarter Pounder hamburgers from McDonald's, and investigators are working quickly to determine which food ingredient is contaminated. McDonald's has withdrawn the ingredients for these burgers and they are not available for sale in some states.

Summary of the situation

CDC, FDA, USDA FSIS and public health officials in several states are investigating an outbreak of E.coli O157:H7 infections. Most people in this outbreak report eating the Quarter Pounder hamburger at McDonald's before getting sick. It is not yet known which specific food ingredient is contaminated.

McDonald's is working with research partners to find out which food ingredient in Quarter Pounders is making people sick. McDonald's has stopped using fresh onion slices and quarter-pound beef patties in several states while the investigation to identify the disease-causing ingredient continues.

Contaminated food

McDonald's Quarter Pounder Hamburgers make people sick, with most illnesses occurring in Colorado and Nebraska.

  • Quarter Pounder hamburgers will be temporarily unavailable in some states.
  • Investigators are working to figure out what ingredient in these hamburgers is making people sick and whether it made its way into other restaurants or stores.
  • McDonald's reported to the CDC that it had stopped using fresh onion slices and quarter-pound beef patties in several states. McDonald's is proactively making these changes while investigators work to confirm the contaminated ingredient. Quarter pound beef patties are only used at Quarter Pounders. Fresh onion slices are primarily used for Quarter Pounder hamburgers and not for other menu items.

What you should do

McDonald's has stopped using fresh onion slices and quarter-pound beef patties in several states to protect its customers while a source of illness is confirmed.

Call your doctor if you have eaten a McDonald's Quarter Pounder hamburger and have severe symptoms E.coli Symptoms:

  • Diarrhea and fever over 38°C
    • Diarrhea for more than 3 days that is not improving
    • Bloody diarrhea
  • Vomiting so much that you can't keep your fluids down
  • Signs of dehydration, such as:
    • Not peeing much
    • Dry mouth and throat
    • Feeling dizzy when standing up

Symptoms of E.coli

  • Most people are infected with Shiga toxin E.coli suffer from severe stomach cramps, diarrhea (often bloody) and vomiting.
    • Symptoms usually begin 3 to 4 days after ingesting the bacteria.
    • Most people recover without treatment in 5 to 7 days.
  • Some people may develop severe kidney problems (hemolytic uremic syndrome, also called HUS) that require hospitalization.
  • More information about E.colisee the E.coli Questions and Answers page.



Content source:

National Center for Emerging and Zoonotic Infectious Diseases (NCEZID)