At least 49 cases of poisoning have been reported in 10 western US states due to an outbreak of intestinal infection (E. coli O157:H7), the Centers for Disease Control and Prevention (CDC) reported.
One of the poisoned people, an elderly man, died. Ten more people were hospitalized, including a child with hemolytic uremic syndrome.
Most of the poisoned people reported eating a Quarter Pounder burger (Royal cheeseburger) at McDonald's. It is not yet clear which ingredient caused the outbreak. McDonald's has stopped using freshly chopped onions and beef patties in several states pending the investigation. The CDC clarifies that the investigation is "moving quickly" and that chopped onions are the likely source of poisoning.
Symptoms of poisoning listed by the CDC include severe stomach cramps, diarrhea (often bloody), and vomiting. Symptoms typically appear three to four days after ingesting the bacteria, and most people recover without treatment within five to seven days, the CDC says.
McDonald's said preliminary investigation results link the tainted onions to "a single supplier that services three distribution centers." Quarter Pounder cheeseburgers have been removed from the menu in the states where the poisoning occurred.
CNBC notes that McDonald's stock price fell about 7% after news of the E. coli outbreak broke.