- 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
- 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).
Anthrax spores can induce three types of illness, depending on how they make contact with the human body.
- Victims breathe in spores floating through the air; the spores then lodge in their lungs.
- Certain cells take the spores to the lymph nodes surrounding the lung. Once they enter the lymph nodes, the spores germinate into bacteria and cause inflammation and enlargement of these lymph nodes.
- Anthrax bacteria then spread from the lymph nodes to sites throughout the body and produce a toxin that can be destructive to organs and is difficult to treat.
- Symptoms can occur within seven days of infection or can take up to 42 days to appear. These symptoms include:
- Fever (temperature greater than 100 degrees Fahrenheit); may be accompanied by chills or night sweats
- Flulike symptoms
- Cough, usually a nonproductive cough; chest discomfort; shortness of breath; fatigue; or muscle aches
- Sore throat, followed by difficulty swallowing; enlarged lymph nodes; headache; nausea; loss of appetite; abdominal distress; vomiting; or diarrhea
- Inhalational anthrax is the most lethal form of an anthrax illness.
- Inhalational anthrax was the cause of all five deaths in the 2001 U.S. postal system attacks.
- Some patients treated with antibiotics can have an initial recovery followed by a relapse once antibiotic therapy has been terminated.
- Inhalational anthrax, like most diseases, is more deadly for people with compromised immune systems.
- Untreated inhalational anthrax has a 90 percent mortality rate.
- The survival rate for inhalational anthrax victims depends on quick diagnosis and treatment with antibiotics.
- The mortality rate is still approximately 75 percent, even with antibiotics.
Anthrax spores enter the body through an open wound or cut, or even through microscopic breakdowns of the skin.
- Symptoms appear within one to seven days after exposure.
- A small sore quickly develops into a blister.
- The blister becomes a skin ulcer, or eschar, and ultimately develops a black scab in the center.
- The sore, blister, and ulcer do not hurt and initially look like a spider bite.
- Cutaneous anthrax is the least deadly form of anthrax.
- The survival rate is 80 percent without treatment and more than 99 percent with treatment.
Gastrointestinal anthrax occurs when anthrax is ingested, usually through meat from anthrax-infected animals.
- First signs of the infection appear within two to five days of exposure.
- Initial symptoms include nausea and loss of appetite.
- Later symptoms include bloody diarrhea, fever, and severe stomach pain.
- Symptoms mirror those for stomachflu, food poisoning, and appendicitis.
If untreated, at least 25 percent of gastrointestinal anthrax cases lead to death.
- To treat someone with an anthrax illness successfully, it must be diagnosed early.
- Early diagnosis is complicated because there is no single screening test to confirm anthrax illness.
- Exposure is confirmed by isolating the anthrax bacteria from the blood, skin lesions, or respiratory secretions or by measuring specific antibodies in the blood.
- Blood tests to confirm an anthraxinfection can take up to 72 hours, since it takes time to isolate a particular bacterium in a blood sample. Some circumstances may produce test results much more quickly. For example, in a severe inhalational case, there may be a large concentration of bacteria in a sample, which may allow technicians to obtain a result in a few hours.
- If inhalational anthrax is suspected, physicians typically obtain a chest X-ray and a CAT scan to confirm their suspicions.
- Nasal swabs can detect the presence of spores but are not a diagnostic tool. A positive swab does not mean a person will develop an anthrax illness and a negative swab does not mean a person will not develop an anthrax illness.
- A nasal swab is only an indicator of whether anthrax spores are present in an area.
What We Don't Know About Anthrax as an Illness
No one knows for sure when treatment must begin to be successful. Some believe antibiotics must start within hours, others say days.
Physicians do not know if children or specific ethnic groups are more vulnerable to anthrax than the general population.
There is still debate about how many spores are needed to infect a person.
All three types of anthrax can be treated with antibiotics. Though ciprofloxacin was first used as a treatment for anthrax during 2001, doxycycline is now the preferred antibiotic for anthrax infection. The reason for this is to prevent other bacteria from developing resistance to ciprofloxacin.
- Antibiotics are prescribed for 60 days.
- Treatment must begin as soon as possible after exposure to be successful because the bacteria produce a toxin in the body that poisons the system quickly and sometimes irreversibly. Antibiotics kill the bacteria but cannot remove the toxin or lessen the effects of any toxin already in the body. There is no antitoxin for the anthrax toxin.
- Those with inhalational anthrax normally have to be hospitalized and on a ventilator to help with breathing.
- Anthrax patients do not have to be isolated since the illness cannot be passed from person to person.
- Which antibiotic is prescribed depends on a patient's age and health, the number of cases in the area being treated, and what is available at the hospital and/or through the Strategic National Stockpile.
- Additional antibiotics for treatment of anthrax are being studied in animal efficacy trials.
- The vaccine is used as a preventive measure for those in high-risk populations, including:
Members of the armed forces deployed to countries suspected of having biological weapons programs
- The current anthrax vaccine is not available to the general public but might be used if an anthrax attack occurs.
- The vaccine is given as a seriesthree shots administered two weeks apart.
- Subsequent injections are given at 6, 12, and 18 months;annual boosters follow.
- The current vaccine can have side effects:
Mild side effects may include soreness, itching, or a lump where the shot was administered; muscle or joint aches; fatigue; or headache
Severe side effects may include a severe allergic reaction (very rare)
There is no evidence that the vaccine has long-term adverse side effects
- In October 2004, HHS awarded a contract to VaxGen Inc. for the manufacture of 75 million doses of a new anthrax vaccine for the Strategic National Stockpile. Evidence from laboratory and animal research has shown that the new vaccine, which uses purified recombinant protective antigen, is effective in providing protection against aerosol exposure to anthrax spores (HHS 2004).
- More information on the clinical trials for new anthrax vaccines, anthrax diagnostic tests, and new antibiotics for anthrax treatment is available at NIAID's website.
Although anthrax cannot be spread from person to person, the spores can travel widely. Following are steps that can be taken to minimize the risk to people who have come into contact with anthrax spores:
- Wash skin with soap and water.
- Start antibiotic treatment if exposure is suspected but not yet confirmed.
- Treat mail with low doses of radiation; irradiating mail kills anthrax spores.
- Use special mail handling procedures, such as wearing gloves and masks, to prevent cutaneous anthrax.
Assessing the Risk
Because it is a naturally occurring bacteria and is studied in thousands of labs, anthrax is readily available.
Anthrax spores are highly stable and can survive in the environment for decades.
Terrorists would have to be highly skilled to mill weapons-grade anthrax spores or distribute them effectively to inflict mass casualties.
Anthrax is highly lethal and may potentially be made more so by engineering it to be resistant to antibiotics.
More information on disasters and emergencies is available at the U.S. Department of Health and Human Service's website: http://www.hhs.gov/emergency