McDonald's E. coli outbreak investigation: What we know

CNN
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An E. coli outbreak linked to McDonald's Quarter Pounders has resulted in at least 49 illnesses, including one death, in 10 states.

Here's what we know.

The U.S. Centers for Disease Control and Prevention issued a food safety alert Tuesday, warning that dozens of people reported eating the Quarter Pounder sandwich at McDonald's before becoming ill.

A specific ingredient has not yet been confirmed to be the cause of the outbreak, but the U.S. Food and Drug Administration says the chopped onions or beef patties on Quarter Pounder sandwiches are the likely source of the contamination.

McDonald's has suspended use of the onions as well as the quarter-pound beef patties in several states, including Colorado, Kansas, Utah and Wyoming, as well as parts of Idaho, Iowa, Missouri, Montana, Nebraska, Nevada, New Mexico and Oklahoma, as the investigation continues said the US Centers for Disease Control and Prevention.

According to the agency, the beef patties are used only for the Quarter Pounders, and the chopped onions are used primarily for the Quarter Pounder and not for other products. Diced onions and other types of beef patties used at McDonald's were not involved in this outbreak, the FDA said.

Escherichia coli, or E. coli, is a common bacteria, but certain species can make you sick. Infections can occur after ingesting the bacteria, often after consuming contaminated food or water. It can also be spread from person to person through poor bathroom hygiene.

People with E. coli infections may experience symptoms such as severe stomach cramps, diarrhea, fever, and vomiting. Symptoms of infection usually begin three to four days after the bacteria is swallowed.

Although most sick people recover within a week without treatment, others may develop serious kidney problems and require hospitalization. According to the CDC, seniors, children under 5 and people with weakened immune systems are most at risk of infection.

E. coli infections from the McDonald's outbreak have resulted in at least 10 hospitalizations, including a child with hemolytic uremic syndrome, a serious complication that can develop from an E. coli infection. An elderly person died.

Most of the illnesses linked to the McDonald's outbreak are in Colorado and Nebraska, according to the CDC, but the agency cautions that the outbreak may extend beyond those states. Illnesses have also been reported in Iowa, Kansas, Missouri, Montana, Oregon, Utah, Wisconsin and Wyoming.

The CDC recommends that people call their doctor if they have recently eaten a McDonald's Quarter Pounder and have severe E. coli symptoms such as fever over 102 and diarrhea, especially bloody diarrhea or diarrhea that has not improved within three days, and Experience vomiting, limited fluid intake or signs of dehydration.

It can take weeks to determine whether an illness is part of an outbreak, but the CDC said the investigation into the McDonald's outbreak was “progressing quickly.”

The agency said the outbreak is expected to grow and that new cases will be reported “on a rolling basis” as scientists are able to establish genetic links between the outbreak strain and the bacteria that cause infections in humans.

According to CDC data, illnesses related to the outbreak were reported from September 27 to October 11. But the start of the outbreak is also likely to be delayed as previous cases come to light, according to an official familiar with the investigation.

Outbreaks like these can also resolve quickly after the tainted food or ingredient is removed from the market. This requires a thorough investigation to ensure that all possible distribution channels have been uncovered and stopped.

The president of McDonald's USA said that it was safe to eat at McDonald's and that the affected ingredients were likely outside the restaurants' supply chain.

“We're very confident that you can go to McDonald's and enjoy our classics” without getting sick, Joe Erlinger, president of McDonald's USA, said Wednesday on NBC's “Today Show.”

According to the CDC, Quarter Pounder sandwiches will be temporarily removed from the McDonald's menu in some states while the company makes some offering changes.

Erlinger said he believes that “if there have been contaminated products in our supply chain, they most likely have already passed through that supply chain,” but acknowledged that the number of reported illnesses could rise as the CDC investigates and traces cases.

“It is our top priority to safely serve customers in every single restaurant, every day,” McDonald's said in a statement Tuesday.

A company fact sheet highlights food safety protocols it says are in place, including daily temperature checks and hourly employee handwashing. It is also noted that Quarter Pounders are prepared to order at temperatures above FDA best practice guidelines.

CDC data released this summer shows that foodborne illnesses are on the rise in the United States. Some illnesses, including E. coli infections, are well above federal goals for reducing foodborne illnesses.

In 2023, there were more than 5 E. coli cases per 100,000 people in the U.S. – a 25% increase from five years earlier and about 40% above target levels.

The Campylobacter bacteria is the most common cause of foodborne illness, causing more than 19 illnesses per 100,000 people – a rate that is 22% higher than five years ago and twice as high as federal goals. Infections from this bacteria are most commonly caused by eating raw or undercooked poultry, according to the CDC, and can cause diarrhea in people.

Salmonella infections have not increased in recent years, but the bacteria still caused about 14 illnesses per 100,000 people in the U.S. in 2023.

According to data from the CDC, Listeria caused about 0.3 illnesses per 100,000 people in the U.S. in 2023, but led to some large, deadly outbreaks that year.

Boar's Head recalled more than 7.2 million pounds of its ready-to-eat liverwurst and some other deli products in late July, resulting in dozens of hospitalizations and at least nine deaths, as well as another recall of nearly 12 million pounds of ready-to-eat meat and poultry products manufactured by BrucePac for consumption have affected schools, retailers and restaurants across the country.

CNN's Nadia Kounang, Carma Hassan, Brenda Goodman and Meg Tirrell contributed to this report.