E. coli Outbreak at McDonald’s Linked to Slivered Onions: What Happened?

In a recent E. coli outbreak affecting 13 states, slivered onions served on McDonald's Quarter Pounders and other menu items have been identified as the primary cause. The U.S. Centers for Disease Control and Prevention (CDC) confirmed that the outbreak has resulted in 90 cases, with 27 hospitalizations and one death. The contaminated onions, supplied by Taylor Farms, were removed from McDonald's restaurants to mitigate the risk​.

The outbreak began with cases reported as early as late September, and McDonald's temporarily pulled Quarter Pounders from menus in 12 states, including Colorado, Kansas, and Utah. The CDC's investigation, which started on October 22, concluded that slivered onions were the “likely source” after beef patties were ruled out following rigorous testing by the Food Safety and Inspection Service (FSIS)​.

How Serious Is the E. coli Risk Right Now?

The contaminated onions were part of a supply chain from Taylor Farms, a major produce supplier. Distributed across McDonald's locations in multiple states, these onions carried the Shiga toxin-producing strain of E. coli (E. coli O157), known for causing severe gastrointestinal symptoms and even kidney failure in some cases. 

This strain of E. coli is particularly virulent and capable of causing serious health issues, such as hemolytic uremic syndrome (HUS), which can lead to kidney failure. The CDC urges anyone experiencing symptoms to seek medical attention promptly​.

Following McDonald's swift action to remove slivered onions from affected locations, the CDC assesses the current risk to the public as "very low." The CDC has confirmed the following cases by state:

• Colorado: 26 cases

• Montana: 29 cases

• Nebraska: 9 cases

• Utah: 4 cases

• Wyoming: 4 cases

Additional cases were found in Michigan, Iowa, Kansas, Missouri, Oregon, and Washington, with one to five cases in each state. These numbers underscore how quickly a single ingredient can affect thousands of customers across multiple states​.

Why Onions Were the Culprit—and Not Beef

Initially, the focus was on the Quarter Pounder’s beef patties, as ground beef has a history of being associated with E. coli outbreaks. However, the Colorado Department of Agriculture tested samples from multiple McDonald's locations and found no traces of E. coli in the beef. 

The CDC's investigation highlighted the complexity of tracing foodborne pathogens in widely distributed food items. In this case, tracking down the slivered onions across McDonald's vast supply chain was critical to quickly identifying and eliminating the contamination source.

Understanding E. coli and Its Risks

E. coli, or Escherichia coli, is a common bacterium, but not all strains are harmful. However, E. coli O157, the strain involved in this outbreak, is particularly dangerous because it produces Shiga toxin, which can cause:

• Severe diarrhea, often bloody

• Stomach cramps and vomiting

• Fever in some cases

• Hemolytic uremic syndrome (HUS), which can lead to kidney failure

Symptoms typically appear three to four days after exposure, though they can develop as quickly as one day or as late as ten days. While most people recover within a week, about 5-10% of those infected, especially young children and older adults, may develop severe complications like HUS​.

The CDC advises anyone who consumed a Quarter Pounder or other onion-containing items at McDonald's and is experiencing symptoms to consult a healthcare provider immediately. Early diagnosis and treatment are essential to avoid complications​.

What Measures Did McDonald's Take?

McDonald’s responded swiftly to the outbreak, working closely with Taylor Farms to recall the slivered onions and halt their use in affected restaurants. The company also temporarily removed the Quarter Pounder from menus in 12 states as a precaution, even though other onion-free items remained available. McDonald’s has a history of stringent food safety protocols and is collaborating with health authorities to ensure the safety of its supply chain.

Joe Erlinger, President of McDonald’s USA, issued a statement affirming the company’s commitment to customer safety: “The decision to remove the affected items was not taken lightly. We acted immediately in close coordination with the CDC to minimize any risk and will continue monitoring the situation closely.” This prompt response aligns with McDonald’s longstanding commitment to food safety and has been praised by public health officials as a model for outbreak management​.

Food Safety and the Wider Industry Impact

This outbreak serves as a stark reminder of the importance of food safety and supply chain transparency in the restaurant industry. Taylor Farms, a leading produce supplier, has initiated a full review of its operations to prevent future incidents. In coordination with the FDA, the company is inspecting its processing centers and working to strengthen its safety protocols.

Implications for the Restaurant Industry

Given the increasing prevalence of foodborne outbreaks, especially with fresh produce, experts emphasize the need for ongoing vigilance. According to the FDA, recent outbreaks involving onions, romaine lettuce, and other raw produce highlight the challenges posed by large, interconnected supply chains. The CDC and FDA have called for more frequent inspections and improved traceability, particularly for high-risk foods like raw vegetables. Enhanced safety measures could significantly reduce the risk of similar outbreaks.

A Look at Past E. coli Outbreaks

The McDonald’s outbreak isn’t the first time slivered onions have been implicated in a foodborne illness. In 2020, an E. coli outbreak linked to onions affected over 1,000 people across 48 states. The outbreak prompted a major recall and intensified scrutiny of the produce industry. According to the CDC, foodborne illnesses cost the U.S. economy billions each year, with E. coli outbreaks representing a significant portion of that impact.

E. coli outbreaks often involve raw produce, which is difficult to sanitize effectively. Unlike meat, which can be cooked to kill bacteria, produce typically reaches the consumer raw. In this context, restaurants like McDonald's increasingly invest in advanced food safety practices to protect their customers and prevent future outbreaks.

Lessons from the Outbreak

This outbreak underscores the importance of rapid response and strong public health measures in managing foodborne illnesses. In coordination with Taylor Farms and federal agencies, McDonald's swift action was critical in containing the spread and minimizing risk to the public. The incident highlights the need for continuous improvements in supply chain transparency and safety protocols across the food industry.

For consumers, this serves as a reminder to stay informed about potential foodborne risks and to seek medical attention if they experience symptoms. As foodborne illnesses continue challenging public health, collaboration among restaurants, suppliers, and health authorities remains essential for ensuring food safety and public well-being.