There are four basic categories of biological warfare agents... They are (1) Pathogens. Pathogens are disease-causing bacteria, viruses, and rick ettsiae. These agents could be used to target food supplies, port facilities, or population centers. Of particular concern is the threat of contagious diseases such as smallpox. Agents that have a long incubation period can infect a large number of people in a short period of time without immediate symptoms or warning signs. (2) Toxins. Toxins are poisons formed as specific secreting products by vegetable or animal organisms such as plants, snakes, spiders, and sea creatures. Toxins act faster and are more stable than live pathogens. Many toxins can be easily produced. (3) Bioregulators. Bioregulators are chemical compounds that are essential for normal psychological and physiological functions. A wide variety of bioregulators is normally present in the human body in extremely minute concentrations. However, these compounds can produce a wide range of harmful effects if they are introduced into the body at higher than normal concentrations or if they are altered. Psychological effects could include exaggerated fear and pain; physiological effects could include rapid unconsciousness and-depending on factors such as dose and route of exposure-could even be lethal. Unlike pathogens that take hours or days to act, bioregulators can produce reactions in minutes. (4) Prions. Prions are composed entirely of microscopic proteins similar to viruses, but without nucleic acid. They are believed to be the infectious agents responsible for degenerative diseases of the nervous system. They infect and propagate by abnormally refolding into a structure which is able to convert normal molecular proteins into abnormally structured forms. Mad cow disease is an example of the effect of prions. (Dept. of the Army, WMD-CST Operations, December 2007, pp. 3-5, 3-6)