Acts of terrorism, usually politically motivated, in which an infectious agent is used against a populace. Most superpowers have biowarfare departments, and so do many so-called rogue states. However, the risk of bioterrorism is possibly greatest from small groups:

Many American cities (including New York City) have practiced civil defense exercises to prepare for anthrax attacks. Other potential pathogenic agents include Alfatoxin, Botulism, Plague, and Ricin.