The United States faces the prospect of events — whether naturally occurring or deliberately caused — that may threaten its security, disrupt its economy, and imperil its citizens. Moreover, we know that despite efforts to prevent and protect against such events, their occurrence is inevitable. Disasters from natural causes (such as wildfires, earthquakes, floods, tornados, and hurricanes as well as human caused events, such as oil spills, hazardous materials releases, and industrial accidents, are facts of life that occur periodically. Within the United States, the events of 11 September 2001 and the anthrax attacks that followed serve as stark reminders of the vulnerability to intentional attacks instigated by those who aspire to harm that nation. The emergence of viruses, such as West Nile and Severe Acute Respiratory Syndrome (SARS), as well as the current threat of an H1N1 pandemic influenza, pose distinct, but related, challenges.