49 people infected! McDonald's hamburger outbreak of E. coli, stock price plunges after hours

McDonald's signature burgers cause E. coli infections in multiple locations in the United States, with the company's stock price plummeting after hours.

On Tuesday, the Centers for Disease Control and Prevention (CDC) in the United States announced that an E. coli outbreak in 10 states has infected 49 people, hospitalized 10, and resulted in 1 death. Those infected all reported having eaten at McDonald's during interviews conducted as part of the investigation.

Following the news, McDonald's stock plunged more than 9% after hours.

The CDC stated that all infected individuals tested positive for the "O157:H7" strain of bacteria. Symptoms of the infection include diarrhea, stomach cramps, vomiting, and fever. The investigation will focus on the onions and beef patties in McDonald's signature "Quarter Pounder" burger.

Later, McDonald's released a statement indicating that the company is taking swift and decisive action in response to the E. coli infections in certain states in the U.S. Preliminary investigation results suggest that some illnesses may be linked to the sliced onions in the Quarter Pounder burger, leading affected restaurants in the region to remove the Quarter Pounder from their menus.

The United States is McDonald's largest market, with over 13,000 company-operated and franchised stores. In the year ending in late June, McDonald's global sales approached nearly $26 billion