If zombies did start roaming the streets, CDC would conduct an investigation much like any other disease outbreak. CDC would provide technical assistance to cities, states, or international partners dealing with a zombie infestation. This assistance might include consultation, lab testing and analysis, patient management and care, tracking of contacts, and infection control (including isolation and quarantine). It’s likely that an investigation of this scenario would seek to accomplish several goals: determine the cause of the illness, the source of the infection/virus/toxin, learn how it is transmitted and how readily it is spread, how to break the cycle of transmission and thus prevent further cases, and how patients can best be treated. Not only would scientists be working to identify the cause and cure of the zombie outbreak, but CDC and other federal agencies would send medical teams and first responders to help those in affected areas (I will be volunteering the young nameless disease detectives for the field work).
Official CDC statement on the coming Zombie Apocalypse
Preparedness 101: Ataxic Neurodegenerative Satiety Deficiency Syndrome