Anthrax
By U.S. Department of Health and Human Services
Posted 3/29/06
Basic Facts
- Scientific name: Bacillus anthracis; rod-shaped bacteria (not a virus)
- Anthrax is the disease that develops after exposure to spores produced by this bacteria.
- The spores can remain dormant for long periods but are still capable of causing infection when someone comes in contact with them by touching or breathing them in.
- Anthrax spores can cause three types of illness, depending on how a person is exposed:
Inhalational (respiratory)—most lethal
Cutaneous (skin)
Gastrointestinal (digestive)
- The anthrax illness is not contagious.
- Anthrax can be treated with antibiotics if diagnosed early.
- An anthrax vaccine exists but is not in widespread use.
Anthrax Spores as a Weapon
Historically, many nations have weaponized anthrax by turning it into a concentrated powder or aerosol form. Generally, anthrax spores tend to clump together and the body can defend itself against them in that form. In a refined state, however, the spores are very dangerous when inhaled.
- Anthrax bacteria are easy to grow in a lab but not easy to refine as a weapon.
- Anthrax spores can be manipulated so they can float through the air and disperse as widely as possible.
- Anthrax spores can be released into the air directly or through a building's heating and ventilation system.
- The 2001 anthrax attacks demonstrated that spores can even be distributed through envelopes in the mail.
- Once aerosolized, anthrax spores cannot be seen by the naked eye or smelled.
- Weaponized anthrax spores can remain in the environment for long periods of time.
What We Don't Know About Anthrax as a Weapon
- Exactly how long the spores remain dangerous is unclear.
- Experts cannot say whether spores can become airborne again after settling. This was one of the issues that made it difficult to assess how the attacks on the U.S. mail system would play out.
- Experts disagree on how many spores are necessary to infect someone. Originally it was believed that it would take up to 10,000; but after the 2001 attacks, experts have revised that number; some believe it takes only a few thousand. For immune-compromised people, there is no safe lower limit.
Identifying an Attack
- An anthrax attack will most likely go undetected until people start becoming sick.
- Tests to confirm the presence of anthrax spores can be conducted on suspicious powder or residue.
- Environmental testing confirms the presence of spores in a building.
- Testing determines the extent of exposure in a building or site (whether anthrax spores are there and how many).
- Initial tests onsite are not as accurate as subsequent lab tests and can sometimes generate false positive results.
- Initial tests may miss smaller quantities of spores.
- Samples must be sent to specialized laboratories for more-definitive tests.
- Receipt of conclusive results can take up to 72 hours because of the complexity of taking the sample (workers must wear protective suits), transporting it to a specialized lab, isolating the bacteria or spores, and producing a test result.
- Blood tests are more reliable in confirming individual cases of anthrax disease.
- Nasal swabs can be a quick tool to confirm the presence of anthrax spores in a given environment (but not to diagnose illness).
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