Anthrax is a disease caused by the bacterium Bacillus anthracis. This bacterium is housed in a hardy spore — a cell that is dormant, but may come to life in the right conditions. Anthrax usually affects livestock, but — as the world has become fully aware — it also infects humans. A naturally occurring disease known since biblical times, anthrax has been developed into a modern biological weapon.

What can you do to protect yourself and your family against anthrax? First, don't panic. The average American's risk of exposure to anthrax remains exceedingly low, despite anthrax spores delivered through the mail in the United States in 2001. Second, arm yourself with information to fully understand this microscopic invader.

Anthrax occurs in three forms, with different signs and symptoms. Signs and symptoms usually occur within seven days of exposure to the bacterium, but, with inhalation anthrax, they can take up to 42 days to appear.

• Cutaneous anthrax. This form of anthrax infects the skin. It is contracted by direct contact with the bacterium, when anthrax spores enter a cut, blister or abrasion on your skin. The infection begins as a raised, sometimes itchy bump resembling an insect or spider bite. But within a day or two, the bump develops into an open, usually painless sore with a black center. In fact, the term "anthrax" comes from the Greek word for coal black, "anthracis," because of this characteristic black scab, which is actually dead tissue. Cutaneous anthrax is the most common form of the disease, accounting for 95 percent of cases, and it's also the mildest form of the disease. With treatment, cutaneous anthrax is fatal in less than 1 percent of cases. However, there is a slight danger that the infection may spread. Signs of spreading include fever, chills and swollen lymph glands central to the area of the sore.

• Gastrointestinal anthrax. It's possible to contract this form of anthrax by eating undercooked meat from an infected animal. Gastrointestinal anthrax causes sores (ulcers) within your intestines — much like the sores that appear on the skin in the cutaneous form. Initial signs and symptoms include nausea, vomiting, loss of appetite and fever, followed by abdominal pain, vomiting of blood and severe, bloody diarrhea. This form of anthrax is extremely rare. It has never been documented in the United States. But it is fatal in 25 percent to 60 percent of cases.
• Inhalation (pulmonary) anthrax. It's possible to contract this form of anthrax by inhaling anthrax spores. Initial signs and symptoms of inhalation anthrax resemble those of the flu — sore throat, mild fever, malaise, fatigue, muscle aches and mild chest discomfort. These first signs and symptoms may last for a few hours or a few days, and they may appear to subside briefly. However, soon afterwards, the disease progresses, producing a high fever, breathing problems and shock. The disease destroys lung tissue and may spread to the brain, causing meningitis. Researchers believe that inhalation anthrax is fatal in approximately 75 percent of cases, even with appropriate treatment. However, of the 11 people infected with inhalation anthrax in the United States in 2001, six survived.

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 are extremely hardy. They're resistant to sunlight and have been known to survive in soil for many years. Anthrax spores remain dormant until they find their way into a host to infect — an animal or a human.

Anthrax primarily affects wild and domestic livestock — such as sheep, cattle, horses, goats and camels — that 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. Naturally occurring anthrax is rare in the United States.

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.

Anthrax as a biological weapon
Before 2001, numerous nations are believed to have experimented with anthrax as a biological weapon, including the United States. The worst documented outbreak of inhalation anthrax in humans occurred in Russia in 1979, when anthrax spores were accidentally released from a military biological weapons facility near the town of Sverdlovsk, killing at least 66 people.

But the average person wasn't aware of this weapon until the fall of 2001, when 22 cases of anthrax infection resulted from letters containing anthrax spores sent via the U.S. Postal Service. Eleven people were infected with cutaneous anthrax. Eleven others were infected with inhalation anthrax, resulting in five deaths.

These cases have heightened concern about the possibility of a large-scale anthrax attack by independent well-funded terrorist groups. The Centers for Disease Control and Prevention has classified anthrax as a Category A bioterrorism agent — which is considered the biggest threat to national security. Anthrax raises concerns as a biological weapon because:

• It's not difficult to obtain. Anthrax is a naturally occurring bacterium, so it's relatively easy to grow or acquire. Samples of anthrax already exist at some research laboratories worldwide. Theoretically, anthrax could also be isolated and grown from the remains of an animal that died of anthrax or from nearby soil.
• It's highly lethal. Experts calculate that 100 kilograms (220 pounds) of anthrax aerosolized over a city on a clear, calm night could kill 130,000 to 3 million people — making such an attack as lethal as a hydrogen bomb. The small size of anthrax spores means they would be likely to infect people indoors as well as those outdoors.
• It's hardy. Anthrax spores are resistant to environmental damage. During World War II, the British government experimented with anthrax on an island off the coast of Scotland. Nearly 40 years later, abundant numbers of spores survived on the island. Cleaning up the island required tons of formaldehyde and seawater.

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 accidentally contaminate themselves. In addition, the release of anthrax spores could be difficult to control because of the wind's variation in direction and velocity, 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 are 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 black 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 may be 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.

How would you know if you've been exposed to anthrax?

For anthrax spores to be used as a biological weapon, they must be processed into a fine, white, powder-like form that disperses in the air. Powder that contains anthrax spores can be mailed in a letter and dispersed when the letter is opened. However, a lot of innocuous substances in our environment come in powder form, from sugar to plaster dust.

If you believe that you're at risk of anthrax exposure — for example, you work in an environment where anthrax has been detected — immediately notify authorities for testing and see a doctor for evaluation and care. If you develop signs and symptoms of the disorder after exposure to animals or animal products in parts of the world where anthrax exists, seek prompt medical attention. Early diagnosis and treatment is crucial.

The damage of a large-scale anthrax attack — if it were to happen — wouldn't be immediately and readily apparent. It would take one or many people seeking treatment for symptoms of anthrax to raise suspicion of an attack. However, in the United States, the Laboratory Response Network (LRN) — a partnership linking about 100 state and local public health laboratories — has been established to quickly diagnose and stop the spread of anthrax.

If authorities suspect exposure to anthrax, field tests can help determine whether a substance contains anthrax spores or whether an area — such as a mailroom, desk or ventilation system — may be contaminated.

In addition, various tests can help doctors determine if a person has the disease.

Field tests
If you find a suspicious powder that you think may contain anthrax, immediately contact local law enforcement authorities. They can decide to bring in a hazardous-material team trained to test for materials such as anthrax.

Wearing protective suits, the team collects samples of the substance and samples from surfaces that may have been contaminated. The samples are then checked for signs of Bacillus anthracis bacteria.

Testing for anthrax occurs in stages. Initial screening tests may be performed in community hospital laboratories, but these tests aren't definitive. A confirmation test must be performed in one of the more specialized state and large metropolitan public health laboratories in the LRN. This involves incubating a sample in a lab dish containing special nutrients that spur any bacteria growth. If anthrax is found, scientists then use a DNA fingerprinting technique to identify the specific strain of anthrax, which gives clues to the geographic origin of an anthrax bacterium. The entire process can take several days.

A variety of rapid field tests could speed up the confirmation process, including one developed by researchers at Mayo Clinic, Rochester, Minn., and Roche Diagnostics of Indianapolis. This rapid test uses polymerase chain reaction technology to detect the DNA of anthrax bacteria in samples collected from people or potentially contaminated areas in less than an hour. However, these tests have yet to receive approval from the Centers for Disease Control and Prevention (CDC) or the Food and Drug Administration (FDA) , so they must be used in conjunction with certified confirmatory tests.

If anthrax is found in the environment, the contaminated areas — such as a mailroom, desk or ventilation system — are sterilized with special washes.

Should you have your home or office checked for anthrax? Probably not. Hand-held home test kits for anthrax can't provide definitive results. Some U.S. companies have hired private firms to test their buildings for anthrax. But, overall, scientists say that random checking of homes and offices is neither necessary nor practical.

Human tests
In addition to examining you and inquiring about your health status and where you work, your doctor can administer tests that may determine if you have the disease. However, there's no screening test that can show if you've been exposed to anthrax.

Your doctor will want to rule out other, much more common conditions that may be causing your signs and symptoms, such as flu (influenza) or pneumonia. He or she may use a rapid flu test to quickly diagnose a case of influenza.

Tests to detect and diagnose anthrax include:

• Skin biopsy. A sample of a suspicious lesion on your skin can be sent to a lab to check for microscopic evidence of cutaneous anthrax.
• Sputum testing. To diagnose inhalation anthrax, respiratory secretions can be cultured to check for the presence of anthrax bacteria.
• Blood tests. If you have signs and symptoms of any form of anthrax, your doctor can take a blood sample and send it to a lab, where it can be cultured to check for the presence of anthrax bacteria. The bacteria should grow in cultures within six to 24 hours, but a laboratory in the Laboratory Response Network must confirm any diagnosis. A blood serology test also is available. This test detects antibodies produced by the body in response to anthrax infection in less than one hour and may be used at hospitals and laboratories outside the LRN. But this test won't be helpful until at least one or two weeks after infection, because it can take that long for antibodies to develop.
• Chest X- ray or computerized tomography (CT) scan. Your doctor may request a chest X-ray or CT scan to help diagnose inhalation anthrax. Since this form of anthrax infects both the lungs and lymph nodes in your chest, there's often a very characteristic appearance on the chest X-ray.
• Endoscopy and stool samples. To diagnose intestinal anthrax, your doctor may examine your throat or intestines with the aid of an endoscope — a thin, flexible tube with a video camera at its tip that can be inserted into your throat or intestines to check for anthrax lesions. Stool samples can be tested for the presence of anthrax bacteria.
• Spinal tap. Sometimes your doctor may need a sample of spinal fluid to confirm a diagnosis of anthrax meningitis. This involves inserting a needle into your spinal canal and drawing out fluid for testing.

If a case of anthrax is suspected or confirmed, doctors have been advised to contact local and state health officials immediately. This helps alert government and health leaders — and the public — of a possible outbreak.

To help local governments prepare for an anthrax attack, the Department of Health and Human Services has provided states, cities and territories with some funding. These funds are helping to assemble emergency response teams and to build better systems for detecting an anthrax attack.

Treatment for all three forms of anthrax depends on oral or intravenous (IV) antibiotics. Treatment is most effective when started as early as possible.

Some strains of anthrax may be more responsive to one type of antibiotic than to another. Ciprofloxacin (Cipro), doxycycline and penicillin are FDA-approved for treatment of anthrax in adults and children. However, your doctor may prescribe other antibiotics or a combination of antibiotics.

These medications work by killing the anthrax bacteria. However, antibiotics may fail in inhalation anthrax once symptoms become severe because the bacteria may already have released large amounts of toxin that aren't affected by antibiotics. Scientists are working to develop an anthrax antitoxin that could neutralize the toxin produced by anthrax bacteria.

If you've been exposed to anthrax, your doctor will likely prescribe a 60-day course of antibiotics. If you have inhalation anthrax, you'll likely be hospitalized and treated with intravenous antibiotics.

Anthrax isn't spread person to person. So a person with anthrax doesn't have to be quarantined or isolated. If you were in contact with someone with anthrax, you'll need to be treated only if you were exposed to a source of anthrax infection.

In addition to treating anthrax, antibiotics can prevent infection in anyone exposed to anthrax. Ciprofloxacin and doxycycline are FDA-approved for post-exposure prevention of anthrax.

The government is working to increase the nation's supply of antibiotics, in the event of a large-scale anthrax attack. Since Sept. 11, 2001, the CDC has expanded the National Pharmaceutical Stockpile (NPS) to include more antibiotics and medical supplies, additional pediatric supplies and antibiotics, as well as antidotes for chemical agents. These supplies are strategically placed so medical supplies can be delivered throughout the United States quickly.

The NPS program is also responsible for storing and transporting the anthrax vaccine, to ensure rapid distribution of vaccines in an emergency.

Anthrax vaccine
An anthrax vaccine for animals was developed in 1881. The FDA approved a human vaccine in 1970, which has mostly been used by military personnel. The human vaccine consists of three shots given two weeks apart followed by three additional shots given at six, 12, and 18 months. Annual booster shots are recommended to maintain immunity.

The human anthrax vaccine doesn't contain live anthrax bacteria, so it can't cause the illness. Side effects may include soreness at the injection site, a flu-like reaction and possibly more serious allergic reactions. The anthrax vaccine isn't recommended for children, pregnant women or older adults. It's an effective, but not a 100 percent protective vaccine.

The vaccine isn't available to the public. Instead, the vaccine is reserved for:

• Active-duty U.S. military personnel who are deployed to areas with high risk of exposure to anthrax
• People who work with anthrax in a laboratory setting
• People who handle potentially infected animal products in areas of the world where anthrax is a threat to livestock
• People who work with imported animal hides or furs from areas with a high incidence of anthrax

Scientists are working to produce a new anthrax vaccine. The new vaccine should require fewer doses and be available in large quantities. The anthrax vaccine for animals can't be used in humans.

Avoiding contact with infected animals
In countries where anthrax is common and vaccination levels of animal herds are low, it's wise to avoid contact with livestock and animal products and to avoid eating meat that hasn't been properly slaughtered and cooked.

Other preventive measures include carefully handling dead animals suspected of having the disease and providing good protection when processing hides, fur, wool or hair.

Keeping the mail safe
Letters containing anthrax have been mailed in the United States. As a result, the U.S. Postal Service continues to take measures to keep the mail safe. For example, state-of-the-art Biohazard Detection Systems were installed in 50 major mail-processing facilities in 2004. These systems provide a new level of protection through early warning if biohazards are detected.

What can you do to protect yourself and your family from anthrax? You can arm yourself with information and answers:

• Should you call your doctor and ask to be vaccinated against anthrax? No. The anthrax vaccine isn't available to the public at this time. Besides, your health may be better served by receiving the influenza vaccine, since the flu kills far more Americans each year than anthrax does.
• Should you call your doctor and ask for a prescription for antibiotics? No. Stocking up on antibiotics for anthrax will only deplete the supply for people who need them for more immediate reasons. Ciprofloxacin and other antibiotics should be used only when there's a medical need as determined by a doctor. In addition, widespread use of antibiotics to prevent anthrax could increase the chances of antibiotic-resistant strains of anthrax and other bacteria developing.
• Should you buy a gas mask? It's unclear whether over-the-counter (OTC) masks would do any good in an anthrax attack. Unlike gas masks worn by hazardous-material teams, most OTC gas masks can't filter out anthrax spores. In addition, anthrax can't be seen or smelled. If it were released, you wouldn't see a cloud of anthrax coming toward you, so you wouldn't know when to put on a gas mask. Even if you were to wear a gas mask, you wouldn't necessarily know when it's safe to remove the mask. Government authorities don't recommend buying gas masks.

Anthrax attacks may have you feeling jittery. However, a few cases of anthrax — as scary as they are — don't represent an epidemic. The most prudent course of action is to keep a healthy perspective and to stay aware of current events.

The anthrax attacks in the United States after Sept. 11, 2001, have increased public awareness of the risk of anthrax and other bioterrorism agents. U.S. government and health officials are on alert for outbreaks of anthrax and have plans in place to address potential large-scale outbreaks.

Government and health officials urge people not to panic but instead to use common sense. To reduce your exposure to anthrax and to feel more secure:

• Report any suspicious substance to local authorities. If you come in contact with a clearly suspicious substance, don't sniff, touch, taste or look closely at it. Don't try to clean it up. Move away from the substance. Alert others in the area about the substance. Leave the area, close any doors, and take actions to prevent others from entering the area. If possible, shut off the area's ventilation system. Those exposed to the substance should wash their hands with soap and water. Then report the substance to local law enforcement authorities. Seek additional instructions for exposed or potentially exposed persons.
• Report any suspicious mail to local authorities. Don't open a suspicious envelope or package. Don't shake or empty the contents. Don't carry the envelope or package, show it to others, or allow others to examine it. Don't sniff, touch, taste or look closely at it or any contents that may have spilled. Instead, put the envelope or package on a stable surface. Then alert others in the area about the suspicious envelope or package. Leave the area, close any doors and take actions to prevent others from entering the area. If possible, shut off the area's ventilation system. Those exposed to the suspicious item should wash their hands with soap and water. Then report the suspicious mail to local authorities. Seek additional instructions for exposed or potentially exposed persons.
• Leave a contaminated area. If there's any question that a room has been contaminated by an unknown, airborne agent, turn off fans or ventilation units in the area. Then leave the area immediately. Close the door or section off the area to prevent others from entering. Summon emergency help. If possible, also shut down all air-handling systems in the building.

If you're concerned about coming in contact with anthrax spores while opening your mail at home or work, wash your hands with soap and water when you're finished to reduce your risk. But realize that the risk of inhalation anthrax from cross-contaminated mail is very low. Consider this: About 85 million pieces of mail passed through the New Jersey and District of Columbia sorting facilities at the same time as the envelopes addressed to two U.S. senators containing anthrax in 2001. Although both of these facilities experienced widespread environmental contamination, health officials didn't find any new cases of anthrax — despite an aggressive search.