McDonald's Quarter Pounder back after E. coli outbreak

McDonald's has resumed Quarter Pounder sales across the U.S. after ruling out its beef patties as the source of an E. coli outbreak that left one dead and many ill.

Following negative test results from the Colorado Department of Agriculture, McDonald's traced the outbreak to slivered onions from supplier Taylor Farms, which it has since dropped.

Quarter Pounders are now served without these onions in affected locations. The CDC advises customers with symptoms to seek medical attention, while McDonald's faces lawsuits and a 7.5% stock drop amid the outbreak.