Anthrax isn't new. Some historians believe anthrax was one of the Egyptian plagues at the time of Moses.
Anthrax disease is caused by a rod-shaped bacterium, Bacillus anthracis, which normally resides as a spore in the soil. These spores remain dormant until they find their way into a host to infect — an animal or a human. Anthrax spores are extremely hardy. They're resistant to sunlight and have been known to survive in soil for decades.
Anthrax spores are odorless, tasteless and invisible to the naked eye. The spores measure about 1 micron in size, the equivalent of one-thousandth of a millimeter.
Anthrax primarily affects farm animals — sheep, cattle, horses, goats and camels — that typically contract intestinal anthrax by eating spores from the soil. Anthrax once was common in most areas where livestock are raised. But in modern times, animal vaccination programs have greatly reduced the natural occurrence of the disease among both animals and humans in much of the world.
Outbreaks of animal anthrax still occur in places that don't have widespread livestock immunization programs, such as Central and South America, eastern and southern Europe, Asia, Africa, the Caribbean and the Middle East.
Historically, most human cases of anthrax occurred as a result of exposure to infected animals or their meat or hides. In fact, anthrax used to be known as woolsorters' disease because people who worked with wool in the 18th century often contracted inhalation anthrax from handling spore-contaminated wool in enclosed factory spaces.
To date, the worst documented outbreak of inhalation anthrax in humans occurred in Russia in 1979. Anthrax spores were accidentally released from a military biological weapons facility near the town of Sverdlovsk, killing at least 66 people.
as a biological weapon
Several countries are believed to have experimented with anthrax as a biological weapon. Others are pursuing germ warfare capabilities. Government officials fear that independent well-funded terrorist groups could also obtain anthrax.
Anthrax raises concerns as a biological weapon because:
People intent on creating widespread anthrax infection would most likely spread anthrax by spraying it or releasing it into a ventilation system. However, making anthrax into a form that can be aerosolized requires growing a large number of spores and converting them into a powder form. That's difficult for perpetrators to do, and they may contaminate themselves. In addition, the release of anthrax spores could be difficult to control once deployed because of the wind, making anthrax a less effective weapon of mass destruction.
Anthrax spores come in different sizes. The smaller the size, the more easily the spores can be inhaled and cause severe illness. Hundreds of strains of anthrax occur naturally, some which are more resistant to antibiotics than others. Genetically altered strains could prove more difficult to treat. However, it takes advanced skill to produce anthrax of uniform size or of increased virulence.
Potentially, animals could be purposely infected with anthrax. But animals with anthrax die very quickly, and their meat turns blackish in color, so it's unlikely that infected animals would ever make it to a meatpacking plant. There's little information available about the risks of food or water being contaminated directly with anthrax spores.
Experts say that biological agents such as anthrax are more of a threat to individuals, who can be infected by anthrax sent through the mail, rather than a threat against large groups.
Anthrax isn't contagious. People who get inhalation anthrax don't exhale spores. There are no reports of the disease spreading from one person to another.
To contract anthrax, you must come in direct contact with anthrax spores. However, you can be exposed to anthrax spores and not become infected. Your risk depends on the amount of exposure and the virulence of the strain of anthrax to which you're exposed. People who test positive for anthrax spores in their nasal passageways, for example, may never develop inhalation anthrax.