Inhalation or respiratory anthrax is an infectious disease caused 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. Historically, the main risk factor for getting anthrax was 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 flower grows) before the actual disease occurs. The process can take up to 60 days.

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

The main form of inhalational anthrax is a bloody infection of the lymph nodes in the chest, a condition called hemorrhagic mediastinitis. Up to half of affected individuals may also have a hemorrhagic meningitis.

There are usually two stages of inhalation anthrax:

• Stage one can last from hours to a few days. Symptoms may resemble a cold or the flu, and can include fever, chills, sweating, fatigue, malaise, headache, cough, shortness of breath, and chest pain.
• Stage two often develops suddenly. Symptoms include fever, severe shortness of breath, and shock.

This list of symptoms is based on a relatively small number of people who have had inhalation anthrax. Additional symptoms may occur.

Tests that may be done include:

• Chest x-ray
• Blood cultures
• Sputum cultures

Initial chest x-rays are likely to show abnormalities such as fluid surrounding the lungs or abnormally wide space between the lungs.

Fluid or blood samples may need to be sent to a lab for more specialized testing.

A spinal tap for CSF culture and a gram stain also may be performed.