The E. coli outbreak linked to McDonald’s Quarter Pounder burgers is likely due to slivered onions, the Centers for Disease Control and Prevention announced this week. The formal confirmation cemented what many had suspected all along, especially after McDonald’s supplier, Taylor Farms, recalled peeled and diced yellow onion products.
Onions were one of the two suspects when the CDC first announced the outbreak earlier this month, with the other being beef patties used in the burgers. According to the CDC, traceback information and epidemiological data collected since the outbreak have all pointed to the onions. McDonald’s says state and federal testing of the beef patties has come back negative.
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The CDC reported Wednesday that 15 more people were identified as sickened in the outbreak; among those 15 people, five were hospitalized. That brings the outbreak to 90 total cases spanning 13 states, including 27 hospitalizations and one death. Among the hospitalizations, two cases involve serious complications that could lead to kidney failure.
Following the outbreak, McDonald’s implemented preventative measures by removing slivered onions from Quarter Pounders from stores in Coloardo, Kansas, and Wyoming, and portions of Iowa, Idaho, Missouri, Montana, Nebraska, New Mexico, Nevada, Oklahoma, and Utah. Diced onions used at McDonald’s were not implicated in the outbreak.
E. coli symptoms typically manifest three to four days after exposure, the CDC notes, causing severe stomach cramps, bloody diarrhea and vomiting lasting approximately five to seven days. While some strains of E. coli naturally exist in human and animal intestines, certain types can cause severe illness when consumed through contaminated food or water.
Food safety experts explain the particular vulnerability of fresh onions to contamination. Food safety lawyer Bill Marler and food scientist Bryan Quoc Le explained to USA Today, “Since onions are served fresh, they can become adulterated with E. coli through fecal contamination, which can occur through wastewater, water in the growing area, fertilizer and the proximity of the growing area to livestock.”
