With the majority of reported cases in Colorado and Nebraska, McDonald's (NYSE:MCD) shares partially recovered from significant losses on Wednesday, falling more than 4% in early trading after the CDC linked the company's Quarter Pounder burgers to an E. coli outbreak spanning multiple states.

With most afflicted people having eaten Quarter Pounder hamburgers, the CDC labeled the outbreak investigation as "fast-moving". As it investigates the contaminated component, the FDA said McDonald's halted using fresh slivered onions and Quarter Pounder beef patties in several areas.

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Moreover, the CDC reports that the epidemic has caused one death and ten hospitalizations spread over ten states. McDonald's Chief Supply Chain Officer for North America responded in an internal memo saying the business had acted "swift and decisively," stopping delivery and removing slivered onions from impacted regions. The menu item was momentarily removed from Colorado, Kansas, Utah, and other affected states by the company.

BTig analyst Peter Saleh said that the epidemic could affect consumer traffic and affect campaigns like the Chicken Big Mac and McRib, scheduled for later this year.

This article first appeared on GuruFocus.