The US Centers for Disease Control have published their plan for keeping America safe during a zombie uprising. It's an exercise in general disaster preparedness, and a clever way of getting people engaged in keeping themselves and their communities safe in the event of unexpected bad stuff.
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).