Anthrax is an acute infectious disease caused by the spore-forming bacterium Bacillus anthracis .
Anthrax most commonly occurs in warm-blooded animals, but can also infect humans. Anthrax is most common in agricultural regions where it occurs in animals. These include South and Central America, Southern and Eastern Europe, Asia, Africa, the Caribbean, and the Middle East. When anthrax affects humans, it is usually due to an occupational exposure to infected animals or their products. Anthrax in animals rarely occurs in the United States.