McDonald's announced Sunday that it will resume selling Quarter Pounder burgers to all its restaurants after tests confirmed that subsamples from both fresh and frozen beef patties tested negative for E. coli.
The outbreak has killed one person and caused more than 70 illnesses.
McDonald's ruled out beef patties as the source of the E. coli outbreak linked to Quarter Pounder hamburgers, citing tests conducted by the Colorado Agriculture Department.
The department stated that it has completed its beef testing and does not expect to receive any additional samples.
"We remain very confident that any contaminated product related to this outbreak has been removed from our supply chain and is out of all McDonald's restaurants," McDonald's Chief Supply Chain Officer Cesar Pina said on Sunday.
The fast food chain had pulled the Quarter Pounder from about one-fifth of its U.S. restaurants, including in Colorado, Utah, Kansas, and Wyoming, and parts of Iowa, Idaho, Missouri, Montana, Nebraska, Nevada, Oklahoma and New Mexico.
McDonald's has now requested its beef suppliers to deliver a fresh supply of patties. All 900 restaurants sourcing onions from Taylor Farms will continue to serve Quarter Pounder burgers without onions. Onions are believed to be the source of the outbreak.
After the Food and Drug Administration identified slivered onions from a single supplier as the most likely source of contamination, McDonald's indefinitely halted sourcing slivered onions from Taylor Farms Colorado Springs, just days after removing their onions from its supply chain.
Last week, distributor U.S. Foods announced that Taylor Farms had recalled four raw onion products as a precaution due to "potential E. coli contamination." The company also urged its customers, including restaurants, to stop using the affected products and to dispose of them immediately.
Onions from Taylor Farms were distributed to stores in Colorado, Kansas, Wyoming, and parts of neighboring states, including some airports, which may explain cases reported in other regions, the company spokesperson noted.
E. coli is eliminated in beef when cooked properly. Quarter Pounder is typically served with raw, slivered onions.
The first case was reported in late September and the Centers for Disease Control and Prevention (CDC) stated that 75 persons across 13 states had been infected with the E. coli strain as of Friday, resulting in one death and 22 hospitalizations, including two cases of hemolytic uremic syndrome, which can lead to kidney failure or death.
Several U.S. fast-food chains removed fresh onions from their menu items last week. Yum! Brands -- which owns Taco Bell, Pizza Hut, and KFC -- confirmed removing fresh onions from their menus in select outlets, even if it said there was no evidence linking E. coli illnesses to its restaurants.
McDonald's is facing multiple lawsuits over the incident, with several customers claiming they fell ill after dining at different outlets.
