What is the E. coli outbreak linked to McDonald's burgers?

One person died and 49 others became ill following an E. coli outbreak linked to McDonald's Quarter Pounder hamburgers, according to a report from the Centers for Disease Control and Prevention (CDC). The outbreak primarily affects residents of the US states of Colorado and Nebraska. The onion slivers used in the burgers are suspected to be the source of the contamination.

What is E. coli?

Escherichia coli (E. coli) is a type of bacteria commonly found in the intestines of humans and animals. While most strains of E. coli are harmless and help maintain gut 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), identified onions as a “likely source,” prompting McDonald's to stop selling Quarter Pounders in 12 states, including Colorado, Nebraska, Kansas and Utah. The fast food chain has also stopped using the onions in question, but investigations are 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 complicated illness, have been hospitalized, while one Colorado resident has died. The CDC's investigation suggests that the actual number of people sick may be higher than reported because many people recover without seeking medical attention. They warned that it was a “rapidly progressing outbreak” with infections occurring primarily among customers who ate the burgers between late September and mid-October.

E. coli: symptoms

The most common symptoms include:

• Severe stomach cramps
• Diarrhea, often bloody
• Vomit
• 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 help if you experience:

• Diarrhea that lasts longer than 3 days
• High fever (over 40°C)
• Bloody diarrhea
• Severe vomiting that makes it impossible to keep fluids down
• Signs of dehydration, such as dry mouth, dizziness or reduced urination