(fxcue news) - McDonald's Corp.'s shares lost around 6 percent in the after-hours trading on Tuesday and are currently trading down around 6 percent in pre-market activity on the NYSE after the U.S. Centers for Disease Control and Prevention or CDC linked severe E. coli outbreak in Mountain West states to the fast food chain's Quarter Pounder hamburgers. The agency has issued a food safety alert against McDonald's Quarter Pounders after one died and 49 people from 10 states got sick from the same strain of E. coli O157:H7. CDC, the U.S. Food and Drug Administration, USDA FSIS, and public health officials in multiple states are investigating the outbreak of E. coli O157:H7 infections to identify the ingredient causing illness. While collaborating with the probe, McDonald's has pulled the suspect ingredients, the slivered onions and beef patties, used for the Quarter Pounder hamburgers temporarily from stores in the affected states. Fresh slivered onions are primarily used on Quarter Pounder hamburgers and not other menu items. The company added that Quarter Pounder hamburgers won't be available for sale in some states as the investigation is ongoing. Escherichia coli or E. coli are bacteria found in many places like the intestines of people and animals. Most kinds of E. coli are harmless and are part of a healthy intestinal tract, but certain strains can make people sick. Most people infected with Shiga toxin-producing E. coli experience severe stomach cramps, diarrhea - often bloody, and vomiting. Symptoms usually start 3 to 4 days after swallowing the bacteria, and most people recover without treatment after 5 to 7 days. Meanwhile, some people may develop serious kidney problems, known as hemolytic uremic syndrome or HUS, and would need to be hospitalized. In the latest E. coli outbreak, most sick people are from Colorado, where 27 got sick, and Nebraska, where 9 got sick. Among them, 10 people have been hospitalized, while one older person in Colorado has died. Additionally, one child is hospitalized with complications of hemolytic uremic syndrome. All impacted people were reported eating at McDonald's before their illness started, and most specifically mentioned eating a Quarter Pounder hamburger. Though the specific ingredient linked to illness has not yet been identified, CDC investigators are focused on two ingredients in particular, such as fresh slivered onions, and fresh beef patties. CDC urged customers, who have severe symptoms of E. coli infection after eating a Quarter Pounder hamburger at McDonald's, to seek health care. McDonald's stock closed Tuesday's regular trading on the NYSE at $314.69, down 0.06 percent. Following the news, the shares fell 5.8 percent in the extended trading to $296.44. In pre-market activity, the shares are at $295.99, down 5.94 percent. For More Such Health News, visit rttnews.com