This video describes the Category A diseases: smallpox, anthrax, botulism, plague, tularemia, and viral hemorrhagic fevers. If these germs were used to intentionally infect people, they would cause the most illness and death. Watch this video to learn how some of these agents have been or can be used as bioterrorist weapons. This video is 03:20 in length.
Centers for Disease Control and Prevention: http://www.cdc.gov/