for dubious purposes added to the growing perception of risk (Henderson, 1999).

Today, no one should doubt the likelihood that the development of weapons of mass destruction lies within the reach of others. Some have taken comfort in the fact that the extensive programs of the United States and the former Soviet Union are believed to have been beyond the capacity of other nations. However, we must recognize that these programs manufactured multiple agents without the benefit of today’s advances in science and technology, which have significantly broadened the field of potentially capable state and nonstate actors.

Numerous commissions have reviewed the threat of bioterrorism in recent years (United States Commission on National Security/21st Century, 2001; National Commission on Terrorism, 2000; Gilmore Commission, 2000). They have uniformly concluded that the United States is vulnerable to a bioterrorist attack and that the likelihood of such an event is high. Nations suspected of having offensive biological warfare programs have been named by the Office of Technology Assessment (U.S. Congress, 1993a), and these same states are often also identified as terrorist sponsors. In light of these agreed-upon threats, why has there been so little concern about this possibility in many quarters, and why has so much surprise been expressed over the outcome of a handful of letters containing anthrax spores dispatched through the mail? One important factor is a lack of familiarity among civilian scientists with the concepts that were the pillar of the old U.S. biowarfare program as well as the Soviet program, particularly in regard to the danger of aerosols. Another reason may be the unexpected use of an envelope as the delivery mechanism for such a deadly manufactured powder as that used in the anthrax letters of 2001, instead of a more stealthy and lethal dissemination system.

Nature of the Threat

When one considers the ways in which the intentional use of a biological agent might be carried out, the first rule should be that we do not know who the possible terrorist will be, his or her motivation, or the wherewithal that may be available for the attack. Thus, attacks intended to incapacitate selected persons and thereby gain attention or to cause serious illness for revenge might employ a very different approach than attacks designed to cause mass casualties. An effort by a disgruntled clinical laboratory worker might have a very different scope from one by a well-funded nonstate organization or a state-sponsored group. Parenthetically, the failure of the Japanese Aum Shinrikyo cult to succeed with biological terrorism should not provide much comfort concerning the need for state sponsorship, given the manifest ineptitude of the perpetrators (Smithson, 2000).

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