Inhalation (or respiratory) anthrax is an infectious disease brought on by breathing in the spores of the bacteria Bacillus anthracis.

Anthrax commonly affects hoofed animals such as sheep and goats, but humans can get sick from anthrax, too. The main risk factor for getting anthrax is some type of contact with contaminated animal hides, hair, bone products, and wool. Inhalation anthrax was most commonly contracted when workers breathed in airborne anthrax spores, which were released during industrial processes such as tanning hides and processing wool.

Breathing in spores means a person has been exposed to the disease, but it doesn't mean they'll get symptoms. The bacteria spores must "germinate," or sprout ( the same way a seed might before a plant grows) before the actual disease occurs. The process usually takes 3 to 14 days, with 43 days being the longest known incubation period.

Once the spores germinate, they release several toxic substances, which cause internal bleeding, swelling, and tissue death.

The main form of inhalation anthrax is a bloody infection of the lymph nodes in the chest, a condition called hemorrhagic mediastinitis. Affected people often also have bloody fuid in their chest cavity called pleural effusions. Up to half of affected individuals may also have hemorrhagic meningitis (infection of the lining of the brain and spinal cord).