Anthrax, a dangerous bacteria that can be deadly, has been used as a tool of domestic terror. Here are some questions and answers about it:

• How do people get anthrax?
In any of three ways: when bacterial spores land on a scratch or other broken skin; when spores of a certain size are inhaled and lodge in lung tissue; when contaminated meat is eaten. Cutaneous, or skin-based, infections account for 95 percent of all cases.

• Does the same germ cause all forms of anthrax?
Yes — the Bacillus anthracis bacterium, which develops from the spore. It is a common soil bacterium. It is not adapted to cause disease, but it secretes toxins poisonous to mammals. As a disease, it is most commonly found in livestock and rarely spreads to humans.

• Is it contagious?
No. Infected people do not spread bacteria or spores to others.

• How is it treated?
A variety of antibiotics are extremely effective for skin anthrax. Among them are doxycycline, penicillin and Cipro.

• How do the three forms differ?
— Pulmonary, or inhalation, anthrax initially resembles a bad cold or flu, with coughing and fever. Symptoms develop between one week to two months after contact. Antibiotics can be effective if the disease is caught at the early stage, but because it is so rare, it is often misdiagnosed as influenza. Severe breathing problems and toxic shock then set in, and death can occur within hours. Without treatment, 90 percent of victims die within a few days of the disease's onset.

— Cutaneous anthrax begins with a small lump resembling an insect bite, which then grows into a large open black pustule, accompanied by fever, swelling and headache. It responds well to antibiotics, but without treatment, about 20 percent of patients die when toxins and bacteria seep into the bloodstream. In most untreated patients, the sore will clear up on its own.

— Intestinal anthrax is rare and also responds well to antibiotics.

• Who is at risk for contracting anthrax?
Ranchers, animal handlers and wool sorters are most at risk for cutaneous infections, with two cases in Texas this year and one in North Dakota in 2000, but none before that since 1992. Tainted meat, the cause of intestinal anthrax, is rare. Inhaled anthrax cases are very rare, with only 18 cases recorded in the United States during the 20th century. Sixty-eight people in the Soviet Union died in 1979 when airborne anthrax spores were accidentally released from a military biological facility.

• How can it be used as a weapon?
Because the inhaled form is both highly lethal and not contagious, anthrax spores sprayed over a specific area make an effective, but containable, battlefield weapon as long as target troops are not vaccinated. However, the spores must be refined to a specific size and often must be further processed for ideal dispersion, capabilities out of the range of amateurs or ill-equipped laboratories.

• Should I take antibiotics now, just in case I might encounter the germ?
No. People should not take antibiotics unless they have reason to think they have been exposed to the bacteria. The treatments can cause side effects and should not be used inappropriately. They also may make it more difficult to fight infection should you become exposed in the future.

• Should I keep a supply of antibiotics at home?
Health experts recommend not, since plenty of medicine is available if needed.

• How long has anthrax been around?
Anthrax is thought to have been one of the Egyptian plagues at the time of Moses. The ancient Romans recorded cases.

• How does it get its name?
"Anthrax" comes from "anthracis," the Greek word for coal, similar to our word "anthracite." The Greeks called it this because of the black scab cutaneous anthrax causes on the skin.

FOX News' Paul Wagenseil and the Associated Press contributed to this report