Anthrax is caused by the bacterium Bacillus anthracis. While anthrax commonly affects hoofed animals such as sheep and goats, humans may acquire this disease as well. Historically, the main risk factor for acquiring inhalation anthrax is breathing in "aerosolized" anthrax spores from industrial processes such as tanning hides and processing wool.

Anthrax is a potential agent for use as a biological weapon or bio-terrorism. While at least 17 nations are believed to have a biological weapons program, it is unknown how many nations or groups are working with anthrax. Most bio-terrorism experts have concluded that it is technologically difficult to use anthrax effectively as a weapon on a large scale.

Inhalation anthrax develops when anthrax spores enter the lungs. A person may have spores in the nasal passages (which indicates exposure), but that doesn't mean they will get the disease. In fact, antibiotic therapy following known or suspected exposure can help prevent the disease. In order for a person to develop the actual disease, the spores must germinate -- a process which may take several days, or even up to 60 days to occur. The spores move to the lymph nodes and once they germinate, lead to the release of several toxic substances (toxins). This results in hemorrhage, swelling, and tissue death.

The main form of inhalational anthrax includes hemorrhagic infection of the lymph nodes in the chest (hemorrhagic mediastinitis). Up to half of affected individuals may also have a hemorrhagic meningitis.

There are usually two stages of inhalation anthrax -- the first stage can last from hours to a few days and is similar to a flu-like illness with fever, headache, cough, shortness of breath, and chest pain.

The second stage often develops suddenly and is notable for shortness of breath, fever, and shock. This second stage is highly fatal in up to 90% of individuals because of the build-up of toxins.

• Initial stage -- fever, chills, sweating, fatigue, malaise, headache, cough, shortness of breath, and chest pain
• Second stage -- 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 be present. Some of the symptoms listed may be absent.

• If inhalation anthrax is suspected, a chest X-ray, blood cultures, and sputum cultures may be obtained. Initial chest x-rays are likely to show abnormalities (e.g., fluid surrounding the lungs or abnormally wide space between the lungs).
• Samples may need to be sent to a special lab for more definitive testing, including PCR, immunoflourescence, and immunohistochemistry.
• Since up to half of affected individuals have a hemorrhagic meningitis, a spinal tap for CSF culture and a gram stain also may be performed.

The mainstay of anthrax treatment is early antibiotic therapy. Several antibiotics are effective, including penicillin, doxycycline, and ciprofloxacin (Cipro). If an outbreak of anthrax is suspected, the antibiotic of choice is ciprofloxacin, until it is known whether the anthrax strain is resistant to any of the other usual antibiotics. Because spores may take up to 60 days to germinate, the length of treatment is usually 60 days.

For inhalation anthrax, people with known or suspected exposure would be given oral antibiotics (pills). If a person develops symptoms of the disease or has a positive test for the disease itself (not just a test for "exposure"), antibiotics would be given intravenously (IV) for 14 days, then orally for the rest of the 60 days.

In the event of a bio-terrorist attack, the National Pharmaceutical stockpile is available to supplement and help provide antibiotics, should a shortage occur.

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.

• Hemorrhagicmeningitis
• Mediastinitis
• Shock
• ARDS (adult respiratory distress syndrome)

Notify your health care provider if you have had an exposure to anthrax and you develop flu-like symptoms as described above. Many of these symptoms are non-specific and may be due to other illnesses, but they should still be evaluated to determine their underlying cause.

In addition, if you have been exposed to anthrax (even if you do not have symptoms), you need to contact your medical provider to determine whether you should receive preventive antibiotics.

There are two primary modes of prevention of anthrax.

Vaccination has been developed and is given in a 6-dose series. This vaccine is mandated for all U.S. military personnel. It is currently not available, nor is it recommended, for use in 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, such as ciprofloxacin (Cipro), penicillin, or doxycycline, depending on the particular strain of anthrax.

THERE IS NO TRANSMISSION OF ANTHRAX FROM PERSON TO PERSON. Household contacts of individuals with anthrax do not need antibiotics unless they have also been exposed to the same source of anthrax.