Important info about recent E. coli outbreak and onions

The U.S. Food and Drug Administration, the U.S. Centers for Disease Control and Prevention and state health agencies are currently investigating an outbreak of E. coli O157:H7 linked to the McDonald’s Quarter Pounder.

Though a specific ingredient has not been identified, beef patties and slivered onions used on that particular product are being investigated as the likely source. Additionally, Taylor Farms Foodservice in Colorado has preemptively and voluntarily recalled yellow onions from its facility in response to the current E. coli outbreak, and the FDA is recommending other food service customers not eat, sell or serve Taylor Farms’ recalled yellow onions.

As the investigation continues, McDonald’s locations in Colorado, portions of Idaho, Iowa, Kansas, Missouri, Montana, Nebraska, Nevada, New Mexico, Oklahoma, Utah and Wyoming have temporarily stopped serving Quarter Pounder beef patties and onions. The FDA stated that diced onions and hamburger patties used at other McDonald’s nationwide were not implicated in the outbreak and are thus still available to customers. Whether the suspected food was sold to other food service customers is unknown.

As of Oct. 25, the McDonald’s E. coli O157:H7 outbreak has sickened 75 people, resulting in 22 hospitalizations and one death across 13 states: Colorado, Iowa, Kansas, Michigan, Missouri, Montana, Nebraska, New Mexico, Oregon, Utah, Washington, Wisconsin and Wyoming. Two of the sickened individuals developed hemolytic uremic syndrome (HUS), a complication of E. coli O157:H7 infection that destroys red blood cells, leading to kidney failure.

The FDA recommends that customers who have recently eaten at McDonald’s and have symptoms of E. coli infection contact their health care providers to report symptoms and obtain care. Symptoms of E. coli infection usually occur three to four days after consuming contaminated food but can occur up to nine days later. Symptoms include severe stomach cramps, diarrhea that is often bloody, fever, nausea or vomiting. Severe infection can result in HUS, high blood pressure, chronic kidney disease and neurological problems.

Although onions have not been confirmed as the source of the current outbreak, they have been implicated in other outbreaks including a salmonella outbreak in 2023. Given this, it is an excellent time to look at how onions are processed and tips to ensure safety when working with onions.

Onions are harvested in the Pacific Northwest from June through August. After harvest, many onions will go into storage to ensure year-round availability. Onions that will be processed are transported by truck to a facility where they are dumped into a hopper. The onions are then conveyed by various equipment to remove debris, such as trash, soil, leaves and rocks, and then are sorted by size before being placed into large bins or bags. From here, onions may be sold to other processors, where they are bagged for retail sale or turned into products such as diced or slivered onions. Onions must be kept dry in a cool location with good ventilation to prevent mold or bacterial growth, so facilities use dry methods for cleaning and sanitizing equipment.

Despite the industry’s care to deliver safe, quality onions to consumers, onions may still harbor pathogens since they do not undergo a “kill step,” such as a cooking process. Additionally, pathogens such as E. coli and salmonella have been known to survive for prolonged periods in foods despite dry or chilled environments.

For these reasons, it is important to handle onions properly to prevent foodborne illness. Once the outer skins have been removed, onions should be washed with running water and cut using a clean cutting board and knife. Do not reuse the same knife and cutting board which were used to remove the skins, unless they have been washed well with soapy water in between. Although onions are often consumed raw, the surest way to ensure safety is to cook them before eating.

The latest information on the current outbreak may be found at the FDA’s website, bit.ly/40kj8hU.

Smith is an associate professor and statewide consumer food specialist for Washington State University in Pullman. Comments or questions may be emailed to food.safety@wsu.edu.