CDC, public health and regulatory officials in several states, the U.S. Food and Drug Administration (FDA), and the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS) are collecting various types of data to diagnose an outbreak of Investigate epidemics in multiple states E.coli O157:H7 infections.

Epidemiological data shows that Quarter Pounder hamburgers served at McDonald’s are contaminated E.coli and make people sick. Initial information from the FDA suggests that onions may be a cause of this outbreak. Investigators from all authorities are working quickly to identify the contaminated ingredient.

Epidemiological data

As of October 22, 49 people had been infected with the outbreak strain E.coli O157:H7 has been reported from 10 states. The illnesses began on dates from September 27, 2024 to October 11, 2024. Of 28 people for whom information is available, 10 were hospitalized and one person developed hemolytic uremic syndrome, a serious condition that leads to kidney failure can. One death of an older adult has been reported in Colorado. This is not the same person with HUS.

The actual number of people sickened in this outbreak is likely much higher than the reported number, and the outbreak may not be limited to those states with known illnesses. This is because many people recover without medical care and are not tested E.coli. Additionally, recent illnesses may go unreported because it typically takes three to four weeks to determine whether 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 became ill. This information provides clues to help investigators identify the source of the outbreak.

The following table provides information about sick people in this outbreak (“n” is the number of people for whom information is available for each population group).

State and local health officials are surveying people about the foods they ate in the week before they became ill. Of the 18 people surveyed, all 18 (100%) reported eating at McDonald’s and 16 people reported eating a beef hamburger. Of 14 people who remember the special beef hamburger they ate at McDonald’s, 12 (86%) say they ate a Quarter Pounder hamburger. Some people affected by this outbreak reported traveling to other states before their illness began. At least one person ate at McDonald’s during their trip.

Traceback information

Investigators are working to determine whether the onion slivers or beef patties in Quarter Pounder burgers are the specific cause of this outbreak.

Preliminary tracking and distribution information reviewed by the FDA indicates that slivers of onion served on Quarter Pounders are a likely source of contamination. The FDA is working quickly to confirm that these onions are a cause of this outbreak and to determine whether these onions were served or sold at other establishments.

FSIS is conducting a tracing of hamburger patties served at McDonald’s to determine whether ground beef is a source of disease.

Public health measures

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. Quarter Pounders are temporarily not available for sale in some states. Call your doctor if you have eaten a McDonald’s Quarter Pounder hamburger and have severe symptoms E.coli Symptoms.