Testing has ruled out beef patties as the source of the outbreak of E. coli poisoning tied to McDonald’s Quarter Pounders, the company has said.
It will resume selling the Quarter Pounder at hundreds of affected restaurants in the coming week.
The US Food and Drug Administration continues to believe that slivered onions from a single supplier are the likely source of contamination, McDonald’s said in a statement.
By Friday, the outbreak had expanded to at least 75 people made ill in 13 states, federal health officials said.
A total of 22 people have been admitted to hospital and two have developed a dangerous kidney disease complication, the Centres for Disease Control and Prevention said. One person has died in Colorado.
Early information analysed by the FDA showed that uncooked slivered onions used on the burgers “are a likely source of contamination”, the agency said.
McDonald’s has confirmed that Taylor Farms, a California-based produce company, was the supplier of the fresh onions used in the restaurants involved in the outbreak, and that they had come from a facility in Colorado Springs, Colorado.
McDonald’s pulled the Quarter Pounder burger from menus in several states — mostly in the Mid West and Mountain states — when the outbreak was announced on Tuesday.
The firm said on Friday that slivered onions from the Colorado Springs facility were distributed to about 900 of its restaurants, including some in transport hubs like airports.
The company said it removed slivered onions sourced from that facility from its supply chain on Tuesday, and added it has decided to stop sourcing onions from the Colorado Springs facility “indefinitely”.
The 900 restaurants that normally received slivered onions from the Colorado Springs site will resume sales of Quarter Pounders without slivered onions, McDonald’s said.
Taylor Farms said on Friday that it had pre-emptively recalled yellow onions sent to customers from its Colorado facility and continues to work with the CDC and the FDA as they investigate.
While it remains unclear if the recalled onions were the source of the outbreak, several other fast-food restaurants — including Taco Bell, Pizza Hut, KFC and Burger King — pulled onions from some menus in certain areas this week.
The outbreak involves infections with E. coli 0157:H7, a type of bacteria that produces a dangerous toxin. It causes about 74,000 infections in the US annually, leading to more than 2,000 hospital admissions and 61 deaths each year, according to the CDC.
Symptoms of E. coli poisoning can occur quickly, within a day or two of eating contaminated food. They typically include fever, vomiting, diarrhoea and signs of dehydration. The infection is especially dangerous for children younger than five, the elderly, the pregnant or people with weakened immune systems.