WASHINGTON — Not generally known for its sense of humor, the Centers for Disease Control and Prevention is renowned more for its clinical observation, tracking things like swine flu. But this week the CDC quietly published a blog alerting Americans that they need to be prepared for any disaster, including a "zombie apocalypse." Dr. Ali Khan is the director of the CDC’s Office of Public Health, Preparedness and Response, now dubbed the "Zombie Task Force." His team was trying to think of a new way to tell p