McDonald's stock price declines following CDC's announcement that E. coli outbreak is connected to Quarter Pounders.

• After the CDC linked the E. coli outbreak to McDonald's Quarter Pounder burgers, the chain's shares fell in extended trading.
• One death and 10 hospitalizations have resulted from the outbreak, according to the CDC.
• So far, 49 cases have been reported in 10 states, with the majority of the illnesses occurring in Colorado and Nebraska, according to the agency.

An E. coli outbreak linked to McDonald's Quarter Pounder burgers has resulted in 10 hospitalizations and one death, causing shares to drop in extended trading on Tuesday.

The CDC stated that 49 cases have been reported in 10 states from Sept. 27 to Oct. 11, with the majority of the illnesses occurring in Colorado and Nebraska. The agency also noted that most of the sick individuals reported consuming a McDonald's Quarter Pounder.

An older adult in Colorado passed away due to hemolytic uremic syndrome, a severe condition that can lead to kidney failure.

The CDC stated that the number of people affected by the outbreak is "probably much greater" than what has been reported so far. The agency explained that many people recover from an E. coli infection without testing for it or receiving medical care. Additionally, it typically takes three to four weeks to determine if a sick patient is part of an outbreak, the CDC added.

The CDC stated that investigators are working to identify the contaminated ingredient, and McDonald's has withdrawn ingredients for the burgers. Early information from the FDA suggests that onions may be the source of the outbreak.

Some states may temporarily not have Quarter Pounder hamburgers, but the CDC has not specified which ones.

McDonald's shares dropped about 9% in after-hours trading Tuesday.

Some strains of E. coli, a bacteria commonly found in the gut of people and animals, can cause illness ranging from mild to severe when consumed through contaminated food or polluted water.

After consuming the bacteria, individuals typically experience symptoms such as stomach cramps, diarrhea, and vomiting, which usually occur three to four days later, according to the CDC. The majority of people recover without treatment within five to seven days.

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