When Chipotle was linked to outbreaks of E. coli and norovirus that sickened hundreds of customers, it took more than two years and required a thorough management shakeup – including a new CEO – to repair the brand’s image and pull its stock out of the gutter.

McDonald's (NYSE:MCD) has confirmed that its beef patties were not to blame for the E. coli outbreak linked to Quarter Pounders that killed one person and sickened 75 others. The fast food giant was informed by the Colorado Department of Agriculture that E.

McDonald’s announced on Sunday that tests in Colorado had ruled out its Quarter Pounder beef patties as the source of a deadly E. coli outbreak, and said that the popular burger would be back on the menu at thousands of locations in a dozen states.