Anthrax is a rare disease of animals and humans caused by bacteria called Bacillus anthracis. Anthrax bacteria occur naturally in the soil in many areas of California and can persist for many years. Livestock such as cattle, sheep, and goats can become infected when they graze on soil that is contaminated with the bacteria. While still alive, animals infected with anthrax cannot transmit the bacteria to other animals or humans. Humans become infected through contact with tissues from an animal that has died of anthrax. In the U.S., human cases of anthrax are seen most frequently in people who handle imported hides and skins of exotic animals, or people who have contact with dead livestock, such as farmers and veterinarians. The disease in humans can vary in severity from skin lesions which respond well to treatment, to more severe, potentially fatal infections of the lungs or gastrointestinal tract. Because of its long life after being dispersed in the environment and its potential for severe, fatal disease, anthrax is considered a possible bioweapon agent.