McDonald's Quarter Pounder is part of a "classics" menu that drives huge sales. That's why the Golden Arches will want to fix an E. coli issue fast.

McDonald’s said it was taking “swift and decisive action” to control the outbreak that has sickened dozens of people, mainly in Colorado and Nebraska.

Health officials are investigating an E. coli outbreak linked to McDonald’s Quarter Pounders in multiple states, the Centers for Disease Control and Prevention said Tuesday.