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The FDA, USDA Food Safety and Inspection Service, and Centers for Disease Control and Prevention are investigating a multistate outbreak of E. coli O157:H7.
Investigators have not definitively identified a source, but most sick people say they had a Quarter Pounder from McDonald’s.
McDonald’s says both the beef patties and slivered onions used in that sandwich are exclusive to that menu item.
According to this outbreak alert from the FDA, “preliminary traceback and distribution information reviewed by the FDA shows that slivered onions served on Quarter Pounders are a likely source of contamination,” the FDA said. “FDA is working quickly to confirm that these onions are a source of this outbreak and to determine if these onions were served or sold at other businesses.”
Other diced onions used at McDonald’s are not implicated.
The outbreak is concentrated in Colorado and nine surrounding states, including Iowa, Kansas, Missouri, Montana, Nebraska, Oregon, Utah, Wisconsin, and Wyoming. As of October 22, 49 people have been sickened, and one has died.
The last illness onset was Oct. 11, according to the investigation.
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