McDonald's restaurants in 12 states, including Oklahoma, temporarily halted sales of the Quarter Pounder until officials found the source: onions

At least 75 people fell ill from the bacterial infection and one person died in Colorado from the O157:H7 strain of E. coli, the Centers for Disease Control and Prevention said Friday. McDonald’s attributed the illnesses to slivered onions, and the Food and Drug Administration indicated that onions might have been the source of the outbreak.