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).

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 may include:

• Blood cultures
• Chest x-ray or CT scan of the chest
• Sputum cultures

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

Fluid or blood samples may be sent to a special laboratory for more testing, including PCR, immunofluorescence, and immunohistochemistry.

A spinal tap to analyze the cerebrospinal fluid (CSF) for infection also may be performed.

Several antibiotics are effective against anthrax, including penicillin, doxycycline, and ciprofloxacin. Inhalation anthrax is usually treated with intravenous (IV) ciprofloxacin plus another antibiotic.

The length of treatment is currently about 60 days for individuals exposed to anthrax, since it may take spores that long to germinate.

The prognosis of inhalation anthrax once it reaches the second stage is poor, even with antibiotic therapy. Up to 90% of cases in the second stage are fatal.

• ARDS (adult respiratory distress syndrome)
• Death
• Hemorrhagic meningitis
• Shock

Notify your health care provider if you have been exposed to anthrax, whether or not you develop symptoms.

An anthrax vaccine is available to select U.S. military personnel, but not the general public.

For individuals who have been truly exposed to anthrax (but have no signs and symptoms of the disease), preventive antibiotics may be offered.

Anthrax is not known to spread from person to person. People living with individuals with anthrax do not need antibiotics unless they have also been exposed to the same source of anthrax.

Inglesby TV, O'Toole T, Henderson DA, et al. Anthrax as a Biological Weapon, 2002. JAMA.160;2002;287:2236-2252.

Lucey DR. Anthrax. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier. 2007: chap 317.

Reissman DB, Whitney EA, Taylor TH Jr, et al. One-Year Health Assessment of Adult Survivors of Bacillus anthracis Infection.JAMA. 2004;291:1994-1998.