Anthrax is an acute infection caused by Bacillus anthracis, a large, gram-positive, spore-forming, aerobic, encapsulated, rod-shaped bacterium. Spores germinate and form bacteria in nutrient-rich environments, whereas bacteria form spores in nutrient-poor environments. The anthrax bacillus produces high levels of two toxins: Edema toxin causes massive edema at the site of germination, and lethal toxin leads to sepsis. Severity of anthrax disease depends on the route of infection and the presence of complications, with case fatality ranging from 5% to 95% if untreated.
The Working Group for Civilian Biodefense considers B. anthracis to be one of the most serious biological threats. Anthrax has been weaponized and used. It can be fairly easily disseminated and causes illness and death. Of the ways that B. anthracis could potentially be used as a biological weapon, an aerosol release would be expected to have the most severe medical and public health outcomes.
Anthrax as a Biological Weapon
Anthrax was successfully used as a biological weapon in the United States in October 2001. Cases resulted from direct or indirect exposure to mail that was deliberately contaminated with anthrax spores. In total, 22 cases were identified, 11 with inhalational (five fatal) and 11 with cutaneous anthrax (seven confirmed, four suspected).
Several countries, including the United States, have had anthrax weaponization programs in the past.