McDonald's Corp MCD shares are facing selling pressure Wednesday after an E. coli outbreak was linked to the restaurant chain's hamburgers. What Happened: The U.S. Centers for Disease Control announced late Tuesday that 49 cases of E. coli have been detected across 10 states. Cases started popping up last month and have continued into October. At least 10 people have been hospitalized so far and there is one reported death. "This is a fast-moving outbreak investigation. Most sick people are reporting eating Quarter Pounder hamburgers from McDonald's and investigators are working quickly to confirm which food ingredient is contaminated. McDonald's has pulled ingredients for these burgers, and they won't be available for sale in some states," the CDC said. The E. coli O157:H7 strain behind the McDonald's outbreak reportedly causes serious illness. It's also the same strain that was responsible for an incident at Jack in the Box in 1993 that killed four people, according to Reuters.