Fatal E. coli outbreak linked to McDonald’s Quarter Pounders

The Centers for Disease Control and Prevention launched an investigation Tuesday into an E. coli outbreak linked to McDonald’s Quarter Pounders, according to a department release. The outbreak killed one person and hospitalized at least 10 more, the department said. Health officials are investigating nearly 50 cases spread in at least 10 states located in the Midwest and West Coast.

Which ingredient is contaminated? The contaminated ingredient has not been identified. Officials believe either the sandwich’s slivered onions or beef patties may be contaminated with the bacteria. Locations in Colorado, Kansas, Utah, and Wyoming stopped using both ingredients. Restaurants in some areas of Idaho, Iowa, Missouri, Montana, Nebraska, Nevada, New Mexico, and Oklahoma have also pulled the onions and patties from service. A McDonald’s statement released Tuesday cited onions from a single supplier as the possible source of the outbreak.

Why these two ingredients? Both the patties and onions are used almost exclusively on the Quarter Pounder and not included on other menu items, according to the CDC.

Dig deeper: Read John Dawson’s report on scientists using a new E. coli strain to produce vanilla flavoring.