A lethal E. coli outbreak linked to slivered onions served on McDonald’s Quarter Pounder burgers has ended, the Centers for Disease Control and Prevention said on Tuesday.
The bacteria strain linked to the outbreak killed one and infected 104 people across 14 states, according to the CDC. At least 34 people were hospitalized in the outbreak and at least four developed hemolytic uremic syndrome, a rare but serious disease that can cause kidney failure, according to the agency.
An E. coli infection can cause symptoms including diarrhea, stomach cramps, vomiting and fever.
The FDA said it tested recalled onions and an environmental sample from a grower, both of which tested positive for a different E. coli strain than the one involved in the outbreak. The agency said no human illnesses were linked to this different strain. Additional samples from the investigation tested negative for E. coli, the FDA said.
The CDC update “reinforces the importance of our values, particularly in moving quickly to do the right thing and to always put people first,” McDonald’s North America Chief Impact Officer Michael Gonda and Chief Supply Chain Officer Cesar Piña said in a statement on Tuesday.
“Federal and state officials have repeatedly said that our immediate actions in October made any risk to the public ‘very low,’ and the risk has remained very low since then,” they added.
Contaminated food products linked to E. coli have been removed from McDonald’s supply chain as of Oct. 22, the company said.
The burger-and-fries chain has invested $100 million in marketing efforts and franchisee support after the outbreak to help revamp the company’s damaged image. McDonald’s visits nosedived in the week after the outbreak was announced.
The real number of people infected with E. coli during the outbreak is likely much higher and could have been from more states, since many recover without being tested for the bacteria or receiving medical care.
A six-year-old girl from Massachusetts died from E. coli, which her mother believes she contracted after eating a McDonald’s cheeseburger before a night of trick-or-treating.
Those with reported illnesses – who ranged in age from one to 88 years old – started experiencing symptoms between Sept. 12 and Oct. 21, the CDC said.
Taylor Farms, McDonald’s slivered onions supplier in the states impacted by the outbreak, recalled its yellow onions. On Oct. 22, McDonald’s paused sales of its Quarter Pounder burgers and removed the onions from impacted locations.
Less than a week later, the world’s largest fast food chain resumed sales of its Quarter Pounder burgers with a different supplier at approximately 900 locations.
Colorado and Nebraska are the states with the highest number of confirmed cases linked to the McDonald’s outbreak. At least 26 people fell ill in Colorado, including one older adult who died, the CDC said. Nebraska has at least nine confirmed cases, the next highest number in a single state.