McDonald's (NYSE:MCD) is facing a significant challenge as an E. coli outbreak linked to its Quarter Pounder burgers has sickened dozens across multiple states. According to the CDC, most cases have been reported in Colorado and Nebraska, and the company has pulled affected products, including slivered onions and patties.

This situation brings to mind the infamous 2015 Chipotle (CMG) E. coli outbreak, which severely damaged that company's reputation and stock. While McDonald's has acted swiftly to mitigate the spread, I will be closely watching how this incident will impact its brand and operations in the long run.

Pre-market, McDonald's shares are down more than 6%, reflecting the market's concerns about the potential long-term effects of the outbreak. With McDonald's set to report earnings next Tuesday, October 29, I'll be closely watching what management has to say about this incident and how it plans to address the situation moving forward.

• Warning! GuruFocus has detected 6 Warning Sign with MCD.

This article first appeared on GuruFocus.