Public health officials have declared an outbreak of E. Coli O157:H7 infections linked to onions served at McDonald’s restaurants to be over, as of December 3, 2024. The outbreak, which began in September 2024, ultimately affected 104 people across 14 states, leading to 34 hospitalizations and, tragically, one death in Colorado.
The Centers for Disease Control and Prevention (CDC), along with the Food and Drug Administration (FDA) and state public health departments, investigated the outbreak. Epidemiologic and traceback data pointed to fresh, slivered onions as the likely source of the infections. McDonald’s and supplier Taylor Farms took steps to remove the implicated onions from their food service locations, actions that public health officials believe have significantly reduced the risk to the public.
Understanding E. Coli Infections
Escherichia coli (E. Coli) is a diverse group of bacteria. While most strains are harmless and live in the intestines of healthy people and animals, some strains, like the Shiga toxin-producing E. Coli O157:H7 involved in this outbreak, can cause severe illness. These harmful strains produce a toxin that can damage the lining of the intestines.
Symptoms of E. Coli infection typically begin 3 to 4 days after exposure to the bacteria and include severe stomach cramps, diarrhea (often bloody), and vomiting. Most individuals recover within 5 to 7 days without specific treatment. However, a small percentage of those infected can develop a serious complication called hemolytic uremic syndrome (HUS).
Hemolytic Uremic Syndrome (HUS)
HUS is a life-threatening condition that affects the kidneys and blood clotting system. It can lead to kidney failure, anemia, and neurological problems. In this outbreak, four individuals developed HUS, and one death was reported in an older adult in Colorado who did not develop HUS. Individuals with HUS require hospitalization and intensive medical care.
What the Investigation Revealed
The outbreak investigation revealed that illnesses began appearing as early as , and continued through . Of the 98 individuals for whom information was available, 34 required hospitalization. Public health investigators used PulseNet, a national surveillance system, to identify illnesses that may be part of this outbreak.
It’s important to note that the actual number of people sickened by this outbreak was likely higher than the reported 104 cases. Many individuals with mild symptoms may not seek medical care or undergo testing for E. Coli, leading to underreporting.
Protecting Yourself from E. Coli
While this particular outbreak is considered over, the CDC emphasizes the importance of taking steps to prevent E. Coli infections. These steps include:
- Clean: Wash your hands thoroughly with soap and water, especially after using the restroom, before preparing food, and after contact with animals. Rinse fruits and vegetables under running water before eating, cutting, or peeling.
- Separate: Keep raw meat, poultry, and seafood separate from foods that won’t be cooked. Use separate cutting boards and utensils for raw and cooked foods.
- Cook: Use a food thermometer to ensure that food is cooked to a safe internal temperature.
- Chill: Refrigerate perishable foods within 2 hours. If the outside temperature is above 90°F, refrigerate within 1 hour. Thaw food in the refrigerator, not on the counter.
McDonald’s Response
McDonald’s cooperated with the investigation and voluntarily removed the implicated onions from its restaurants. The company has stated its commitment to food safety and has implemented measures to prevent similar outbreaks in the future. Taylor Farms, the supplier of the onions, also took action to remove the product from the market.
Looking Ahead
The CDC continues to monitor for E. Coli infections and investigates outbreaks as they occur. The agency emphasizes the importance of reporting suspected foodborne illnesses to local health departments. While the risk associated with this specific outbreak is now considered low, vigilance and adherence to food safety practices remain crucial for protecting public health.
For more information about E. Coli infections, visit the CDC’s website at https://www.cdc.gov/ecoli/about/index.html.
