Bacillus anthracis is a gram-positive bacteria that can cause the disease anthrax. It forms spores that can lie dormant in the environment for decades before entering an animal or human and becoming active. Anthrax infection in humans can occur through inhalation, ingestion, or skin contact. While rare, anthrax remains a bioterrorism threat due to its ability to be easily produced and stored for long periods of time. Prompt antibiotic treatment and vaccination can prevent illness, but anthrax poses a risk for mass casualties if used as a biological weapon.