Biodefense refers to measures to restore biosecurity to a group of organisms who are, or may be, subject to biological threats or infectious diseases. Biodefense is frequently discussed in the context of biowar or bioterrorism, and is generally considered a military or emergency response term. Biodefense applies to two distinct target populations: civilian non-combatant and military combatant (troops in the field). Protection of water supplies and food supplies are often a critical part of biodefense. Military Troops in the field Military biodefense in the United States began with the United States Army Medical Unit (USAMU) at Fort Detrick, Maryland, in 1956. (In contrast to the U.S. Army Biological Warfare Laboratories [1943–1969], also at Fort Detrick, the USAMU's mission was purely to develop defensive measures against bio-agents, as opposed to weapons development.) The USAMU was disestablished in 1969 and succeeded by today's United States Army Medical Research Institute of Infectious Diseases (USAMRIID). The United States Department of Defense (or "DoD") has focused since at least 1998 on the development and application of vaccine-based biodefenses. In a July 2001 report commissioned by the DoD, the "DoD-critical products" were stated as vaccines against anthrax (AVA and Next Generation), smallpox, plague, tularemia, botulinum, ricin, and equine encephalitis. Note that two of these targets are toxins (botulinum and ricin) while the remainder are infectious agents. Civilian Role of public health and disease surveillance It's extremely important to note that all of the classical and modern biological weapons organisms are animal diseases, the only exception being smallpox. Thus, in any use of biological weapons, it is highly likely that animals will become ill either simultaneously with, or perhaps earlier than humans. Indeed, in the largest biological weapons accident known–the anthrax outbreak in Sverdlovsk (now Yekaterinburg) in the Soviet Union in 1979, sheep became ill with anthrax as far as 200 kilometers from the release point of the organism from a military facility in the southeastern portion of the city (known as Compound 19 and still off limits to visitors today, see Sverdlovsk anthrax leak). Thus, a robust surveillance system involving human clinicians and veterinarians may identify a bioweapons attack early in the course of an epidemic, permitting the prophylaxis of disease in the vast majority of people (and/or animals) exposed but not yet ill. For example, in the case of anthrax, it is likely that by 24–36 hours after an attack, some small percentage of individuals