The intentional or unintentional introduction of a pathogen in an urban setting presents severe communication challenges. Risk communication--a science-based approach for communicating effectively in high-concern situations--provides a set of principles and tools for meeting those challenges. A brief overview of the risk communication theoretical perspective and basic risk communication models is presented here, and the risk communication perspective is applied to the West Nile virus epidemic in New York City in 1999 and 2000 and to a possible bioterrorist event. The purpose is to provide practical information on how perceptions of the risks associated with a disease outbreak might be perceived and how communications would be best managed.