November 13, 2024 — CDC, public health and regulatory officials in several states, the U.S. Food and Drug Administration (FDA) are collecting different types of data to investigate a multistate outbreak of E. coli O157:H7 infections.
Epidemiologic and traceback data show that fresh, slivered onions served at McDonald’s were the likely source of this outbreak.
Epidemiologic data
As of November 13, a total of 104 people infected with the outbreak strain of E. coli O157:H7 have been reported from 14 states. Illnesses started on dates ranging from September 12, 2024, to October 21, 2024.
Of 98 people with information available, 34 have been hospitalized, and 4 people developed hemolytic uremic syndrome, a serious condition that can cause kidney failure. One death has been reported from an older adult in Colorado. This person is not one of those who developed HUS.
The true number of sick people in this outbreak is likely much higher than the number reported, and the outbreak may not be limited to the states with known illnesses. This is because many people recover without medical care and are not tested for E. coli. In addition, recent illnesses may not yet be reported as it usually takes 3 to 4 weeks to determine if a sick person is part of an outbreak.
Public health officials collect many different types of information from sick people, including their age, race, ethnicity, other demographics, and the foods they ate in the week before they got sick. This information provides clues to help investigators identify the source of the outbreak.
The table below has information about sick people in this outbreak (“n” is the number of people with information available for each demographic).
State and local public health officials are interviewing people about the foods they ate in the week before they got sick. Of the 81 people interviewed, 80 (99%) report eating at McDonald’s. Seventy-five people were able to remember specific menu items they ate at McDonald’s. Of 75 people with information, 63 (84%) reported a menu item containing fresh slivered onions.
Some people in this outbreak reported traveling to other states before their illness started. At least seven people ate at McDonald’s during their travel.
Laboratory information
FDA tested recalled onions and one sample tested positive for non-O157:H7 Shiga toxin-producing E. coli. The E.coli found in onions was not the outbreak strain and no human illnesses have been linked to this strain. Additional testing results will be released when available by FDA.
Public health actions
Because these onions are recalled and past shelf life, it is not necessary to avoid eating onions or other foods made with onions. Call your healthcare provider if you have severe E. coli symptoms.
