What Is It?

Scientifically known as Bacillus anthracis, this rod-shaped bacterium infects humans through the respiratory system, skin or digestive tract. While it is not contagious, depending on the method of infection, anthrax can be highly lethal. Simply made, anthrax is not easy to disseminate.

Weaponization of anthrax -- the more sophisticated process -- is needed to easily disseminate it. During this process, the bacterium is refined so it's reduced to its most infective size. This allows it to travel long distances in the air and to be inhaled.

Inhalation anthrax has a fatality rate of 90 percent.

Currently researched at more than 2,000 U.S. labs, it can remain in a dormant spore form for decades before becoming active again.

Germany tried to use anthrax as a weapon during World War I. During World War II, most warring parties had biowarfare programs; Japan used anthrax in China. During the Cold War, both the United States and the Soviet Union set up large biowarfare programs. Although the United States dismantled its biowarfare program in 1969, the Soviets carried on, and in 1979, an anthrax leak from a Soviet weapons plant killed more than 60 people.

The American public learned a few lessons about anthrax in October 2001, following the Sept. 11 terrorist attacks. Four contaminated letters to the New York Post, NBC's Tom Brokaw, then-Senate Majority Leader Tom Daschle and Sen. Patrick Leahy of Vermont carried a more potent form of anthrax. Confirmed anthrax cases at American Media in Florida and at the New York offices of CBS and ABC suggest that letters were also sent to these offices. Twenty-three people contracted anthrax from these letters -- 11 postal workers and 8 media workers. Three other victims in Connecticut, New Jersey and New York City also died from exposure. To this day, there are no suspects.

How Is It Spread?

In natural-acquired cases, organisms usually gain entrance through skin wounds, causing a localized infection, but they may also be inhaled or ingested. Intentional release by terrorist groups would probably involve the aerosol route, as the spore form of anthrax is very stable and ideal for this type of transmission. However, as seen in the fall of 2001, anthrax can also be used as a weapon in the powder form, sent through the mail or through other means.

What Are the Symptoms of Exposure?

Inhalation anthrax -- Once inhaled, the tiny anthrax spores -- less than one-twentieth the diameter of a human hair, enter the lungs' air sacs, where blood is oxygenated. It's not known exactly how many spores are needed to infect a human. From the lungs, the infection spreads to the lymph nodes in the chest, and within hours or days, the bacteria begin producing deadly toxin.

There are two phases of inhalation anthrax infection, with a short recovery-like period sometimes following the first phase: the first causes flu-like symptoms such as fever, nausea, vomiting, aches and pains and fatigue, which usually appear in one to seven days after exposure; and the second includes respiratory distress and failure, shock and sometimes death, and is usually reached within two to four days of the onset of symptoms.

Cutaneous anthrax -- infects humans though the skin or through the digestive system. Cutaneous infections occur when open wounds or cuts come in contact with the anthrax bacterium. A visible infection, such as sores or black scabs, appears one to seven days after exposure.

Gastrointestinal anthrax -- results from ingestion of meat contaminated with anthrax bacteria, causes symptoms within two to five days and includes stomach pain, diarrhea, fever and septicemia (bacteria in the blood).

How Is It Treated?

Inhalation anthrax -- long-term treatment with antibiotics can reduce the 90 percent fatality rate to 30 percent. Treatment is most successful if begun before the toxin is released.

An anthrax vaccine exists but is only effective if the first of six inoculations is given at least four weeks before exposure. Vaccines are currently only given to those considered at an increased risk of exposure, such as lab workers or military personnel. It consists of three injections given two weeks apart, followed by three more injections at six, 12 and 18 months. Annual booster injections are recommended to maintain immunity.

Ciprofloxacin is the best-known antibiotic, but penicillin and doxycycline have also been effective against the forms in the mailed letters. Amoxocillan can also be used. Many of these antibiotics are available in pharmacies with a prescription. A May 2002 study said that a treatment involving shots of vaccine plus a 60-day regimen of several antibiotics is more effective than simply taking Cipro.

Some scientists say a special enzyme developed by Rockefeller University biologists may also be an effective antidote, if injected quickly enough. But more tests must be completed before the enzyme can be used as a drug.

Cutaneous anthrax -- treatable with antibiotics.

Gastrointestinal anthrax -- has about a 50 percent fatality rate. Antibiotic treatment greatly reduces this number.

The federal government only has enough vaccine for about 4,000 people, and it requires six painful shots over 18 months. In 1997, the Pentagon decided to vaccinate all military personnel, but in June 2002, the Bush administration shifted course, deciding to vaccinate some troops while stockpiling more vaccine in America to prepare for possible domestic attacks. Having administered the six-shot series to about 69,000 troops, the U.S. government now plans to vaccinate only those troops who spend at least 15 days a year in high-threat areas such as the Persian Gulf, the Korean Peninsula and possibly Afghanistan.

Who Has It/Where Can It Be Found?

Anthrax is widely available and is even naturally occurring in domestic livestock and certain wildlife. It's currently studied at more than 2,000 U.S. facilities. It's a bacteria, often found naturally in the soil as close to home as rural Texas, Oklahoma and near the Mississippi. It's also made in research and military labs.

In a remote corner of the Nevada desert, in a highly restricted area once used to test nuclear bombs, the U.S. government has been running a secret experiment called Project Bachus -- a small germ warfare factory. U.S. officials say they built it to better understand how to detect similar operations in places like Iraq or Afghanistan or even by terrorists here at home. Technicians grew several pounds of a harmless bacterium with characteristics similar to deadly anthrax.

Government officials say the United States no longer has a bioweapons program, although the military continues to use anthrax for defensive purposes such as vaccine development. More than a dozen other countries may have programs that could make anthrax, including big powers -- Russia, China, India; unfriendly countries -- Iraq, Iran, Syria, Libya, North Korea, Cuba; and American allies -- Israel, Egypt, South Africa, South Korea. More than 40 germ banks in the United States and around the world supply anthrax for scientific research.