One person died and 49 others became ill after an E. coli outbreak linked to McDonald’s Quarter Pounder burgers, according to a report from the Centers for Disease Control and Prevention (CDC). The outbreak has mainly affected residents of the US states of Colorado and Nebraska. It is suspected that the chopped onions used in the burgers are the source of contamination.

What is E.coli?

Escherichia coli (E. coli) is a type of bacteria that is commonly found in the intestines of humans and animals. While most E. coli strains are harmless and help maintain intestinal health, some can cause serious foodborne illness.

E. coli outbreak at McDonald’s: What’s happening?

The CDC, along with the Food and Drug Administration (FDA), have identified onions as a “likely source,” leading McDonald’s to suspend sales of Quarter Pounders in twelve states, including Colorado, Nebraska, Kansas and Utah. The fast food chain has also stopped using the onions in question, although research is underway to determine whether the hamburger patties themselves could also be contributing to the outbreak. The outbreak was linked to E. coli O157.

So far, 10 people, including a child with a complicating illness, have been hospitalized, while a Colorado resident has died. The CDC’s research shows that the actual number of sick people may be higher than reported because many people recover without seeking medical care. They warned it was a “rapidly evolving outbreak”, with infections mainly occurring among customers who ate the burgers between late September and mid-October.

E. coli: Symptoms

Common symptoms include:

• Severe stomach cramps
• Diarrhoea, often bloody
• Vomiting
• Fever, although not always present and usually mild when it occurs

Symptoms usually appear three to four days after exposure to the bacteria, but can sometimes begin as early as one day or as late as ten days. Most people recover within five to seven days. In severe cases, E. coli can lead to a serious complication called hemolytic uremic syndrome (HUS), which affects the kidneys and may require hospitalization.

The CDC recommends seeking medical attention if you experience:

• Diarrhea that lasts more than 3 days
• High fever (over 102 degrees F)
• Bloody diarrhea
• Severe vomiting that prevents fluids from being kept down
• Signs of dehydration, such as dry mouth, dizziness, or decreased urination