E. coli outbreak at McDonald’s: How did it spread and who is most vulnerable?

About 50 people have been sickened so far after a food poisoning outbreak linked to McDonald’s Quarter Pounders was reported in the US. The outbreak has been linked to a common type of E. coli bacteria that can cause serious illness and death.

What is E.coli?

E. coli is a type of bacteria found in the environment, including water, food, and in the intestines of people and animals. There are many types of harmless E. coli, but a few types can make people seriously ill.

The McDonald’s outbreak is caused by E. coli O157:H7, which produces a toxin that causes dangerous diarrhea and can lead to kidney failure and other serious problems.

What caused the McDonald’s outbreak?

Preliminary research indicates that raw chopped onions served on Quarter Pounders are a likely source of the outbreak.

How does it spread?

People can become ill from E. coli poisoning if they consume contaminated food or through contact with animals, the environment, or other people who are infected.

Reports indicate that health officials initially focused on fresh chopped onions and beef patties as possible sources of the McDonald’s outbreak. But the beef patties are an unlikely source because of federal meat testing requirements and McDonald’s protocols that call for cooking them at a temperature that kills the bacteria. The onions are served raw.

Who is more vulnerable?

Young children, the elderly or people with a weakened immune system are particularly vulnerable.

What are the symptoms of E. coli poisoning?

Symptoms come on quickly, within a day or two of eating contaminated food, and typically include fever, vomiting, diarrhea or bloody diarrhea, and signs of dehydration — little or no urination, increased thirst, and dizziness.

The infection can cause some form of serious kidney damage, especially in children under 5 years of age. E coli poisoning in young children requires immediate medical attention.

How common is E. coli in the US?

The type of bacteria involved in this outbreak causes about 74,000 infections in the U.S. each year, leading to more than 2,000 hospitalizations and 61 deaths annually, according to the CDC. Overall, E. coli infections in 2023 were lower than in recent years and cases of serious kidney injuries caused by the bacteria remained stable, according to the latest federal data.