McDonald’s (MCD) is facing significant challenges following an E. coli outbreak that led to a 7% drop in its stock on Tuesday.

About 2,700 U.S. restaurants are temporarily not serving Quarter Pounders or onions as a precaution.

The CDC has issued a food safety alert, and there are currently 49 reported cases linked to the outbreak, including one death.

McDonald’s is investigating the source, suspecting onions might be involved, as the beef patties come from multiple suppliers.

This incident echoes past food safety issues faced by Chipotle (CMG), but analysts believe it’s premature to make direct comparisons, Yahoo Finance has reported.

The outbreak occurs as McDonald’s contends with declining same-store sales and increased competition.

The company is working with health authorities to address the situation and plans to provide updates, with Q3 results expected next Tuesday.

Written by B.C. Begley