Biological threats that could result in catastrophic consequences exist in many forms and arise from multiple sources. For example, several known biological agents could be made into aerosolized weapons and intentionally released in a transportation hub or other populated urban setting, introduced into the agricultural infrastructure and food supply, or used to contaminate the water supply. Concerned with the threat of bioterrorism, in 2004, the White House released HSPD-10, which outlines four pillars of the biodefense enterprise and discusses various federal efforts and responsibilities that help to support it. The biodefense enterprise is the whole combination of systems at every level of government and the private sector that can contribute to protecting the nation and its citizens from potentially catastrophic effects of a biological event. It is composed of a complex collection of federal, state, local, tribal, territorial, and private resources, programs, and initiatives, designed for different purposes and dedicated to mitigating various risks, both natural and intentional.