Anthrax is a serious disease caused by the bacterium Bacillus anthracis. While anthrax most commonly occurs in animals (such as cattle, sheep, and antelopes), it can affect humans. There are three major types of anthrax: cutaneous (skin) anthrax, inhalation anthrax, and gastrointestinal anthrax. Anthrax transmission typically occurs in one of two ways: from animals, or as the result of a biological weapon. Anthrax treatment usually involves antibiotics and providing relief of symptoms and complications as the body fights the anthrax bacteria.