Feces, dead horses, and fleas. Evolution of the hostile use of biological agents.

Selected events in the history of biological weapons are highlighted to increase physicians' awareness of the threat of biological weapons. The hostile use of biological substances originated in antiquity and pervades the history of human conflict. Although difficult to verify at times, the use of such weaponry has not been limited to national militaries. Disgruntled civilians and even physicians have used biological weapons to promote their interests. Their potency, cost-effectiveness, and the ability to manufacture and deploy them with little sophistication, or under the semblance of legitimate commercial endeavors, will ensure that biological weapons remain a constant threat to public health.