Best Of Counterterrorism & Security
Original article from summer 1998 issue

Anthrax as a Weapon of Terrorism
By Michael A. Feeney, R.Ph., J.D., C.H.O.

The opinions and interpretations by the author are his own and do not necessarily reflect those of the Massachusetts Department of Public Health, its Commissioner, or any of its agents or governing authorities.

In the wake of the Persian Gulf War, Oklahoma City bombing and use of sarin by Aum Shinrikyo in Tokyo, the potential use of nuclear, biological and chemical (NBC) weapons by terrorists within the United States has come to the attention of the print and electronic media. As recently as June 14, 1998, 60 Minutes ran a story concerning the use of anthrax as a weapon in major cities such as New York and Boston. Earlier this year, Secretary William Cohen appeared on the This Week program using a 5 lb. bag of sugar to demonstrate the amount of anthrax bacillus necessary to devastate a major metropolitan city.

While much information is being presented about the threat of anthrax as a weapon of mass destruction, little information is being disseminated concerning the reasons why anthrax can be used as a weapon or how to respond to its use.  While anthrax is in its simplest term, a hazardous material, it is a disease that has had a long standing presence in human history.  This article is an effort to consolidate the mass of information concerning anthrax from multiple unclassified sources.

Anthrax in History

The disease of anthrax infections has a long history with mankind. It is a bacterium that primarily effects grazing animals, such as sheep, cattle, goats and horses.  Anthrax was known to ancient cultures, and is described to have killed 40,000 horses and 100,000 cattle in the possession of the Huns during their movement across Eurasia in 80 AD. As a considerable bane to the European livestock trade, throughout the 18th and 19th century, much effort was put into the identification and prevention of anthrax in animals.  Anthrax (scientific name Bacillus anthracis) was the first microorganism identified as the cause of a specific disease by Dr. Robert Koch in 1876. Later that year Dr. Koch was growing Anthrax bacillus in his laboratory. Within the decade, Louis Pasteur for use in livestock developed a viable anthrax vaccine.

World War I saw the possible introduction of anthrax as a weapon against livestock and transportation animals. A clandestine biological research laboratory was set up in Baltimore, MD by the German government in 1915.  A number of suspected uses of anthrax by the German government during World War I were alleged, but not well documented. Japan, Great Britain, and the United States all proceeded with research into the use of anthrax bacillus as a weapon in World War II.  While no combatants used anthrax during this war, the Anthrax bacillus was both tested on animals and allied prisoners. Weapon delivery systems were also developed.

The former Soviet Union also developed a biological research program during the Cold War.  The accidental release of anthrax from a secret bio-weapons research facility in Sverdlovsk, USSR resulted in the death of 66 of 77 diagnosed cases.

With the establishment of a biological weapons research facility in al-Hakim, Iraq, in 1988, concerns over the use of anthrax during the Persian Gulf War resulted in U.S. troops being vaccinated.  It is not believed that anthrax was used by the Iraqi armed forces.

In 1993, the Aum Shrinkyo cult attempted to release anthrax spores in downtown Tokyo one month prior to the nerve gas attack. This incident marks the first instance of anthrax being used as a weapon against a civilian population.

Anthrax as a Disease

Anthrax is caused by bacteria that are a rod shaped organism, Bacillus anthracis.  Anthrax is a non-motile organism between 1-5 micrometers in length. Upon exposure to air, anthrax forms a spore, which can become airborne to cause infection to exposed individuals. Anthrax spores can cause disease by coming in contact with abraded skin or wounds; inhalation; or ingestion.  As anthrax reproduces, it releases three virulence factors: lethal factor, edema factor and antiphagocytic factor.  Each of these substances enhances the destruction of cells and resists the immune system.  Damage to the body depends on which organ system the anthrax spore colonizes. Antibiotics have long been used to treat skin anthrax and have been shown to be effective in the laboratory against the anthrax bacillus.  While effective against the bacillus, antibiotics do not reduce the amount of virulence factor in victims. Even with antibiotic treatment, the virulence factors continue to cause damage within the body.

Skin (cutaneous) anthrax is a disease that starts with the spore colonizing the skin through an abrasion, cut or wound.  After exposure to the spore, one to five days will pass before the presentation of symptoms (the incubation period). The disease starts as a small lesion, which grows into a puss-filled blister (a vesicle). The vesicle then turns coal black scab (an eschar).  Symptoms include fever, malaise and headache. The eschar heals within two-three weeks with treatment. Mortality of cutaneous anthrax victims range from 20-25 % without treatment, less than one percent with treatment.

Pulmonary anthrax starts with inhalation of anthrax spores.  The U.S. Army estimates that inhalation of 8,000-50,000 spores can cause infection. After an incubation period of one to seven days, an exposed individual develops flu-like symptoms [malaise, fatigue, myalgia (body ache), fever and non-productive cough] that persist for two to three days. After a leveling of symptoms or improvement, severe respiratory distress with symptoms of dyspnea (difficulty breathing), stridor (grating sound on inspiration that is associated with upper respiratory obstruction), cyanosis (bluish color in skin due to lack of O2 exchange due to lung damage), increased chest pain, tachycardia (excessively rapid heart rate) and diaphoresis (excessive sweating) develop.  Fifty percent of victims will develop meningitis. Within twenty-four to thirty-six hours, the victim experiences the rapid onset of shock and subsequent death. Inhalation anthrax has a mortality of 95-100% despite antibiotic treatment.

Ingestion anthrax has an incubation period of 2-5 days.  Symptoms include nausea, vomiting, fever and severe abdominal pain. Ingestion anthrax has a mortality of 95-100 % despite antibiotic treatment.

The Occurrence Worldwide of Anthrax

Anthrax exists in soil as a spore. Under certain condition, the anthrax spore can remain viable in soil for decades. After conducting open-air anthrax weapons research on Gruinard Island in Scotland in 1941, the British government banned human entry for over fifty years.

Anthrax occurs worldwide, reported in 82 countries.  Human cases of anthrax are reported regularly in countries in the Middle East, Africa and the former Soviet Union.  Cases of animal anthrax in the United States occur in Texas, Louisiana, Mississippi, Oklahoma and South Dakota.  Cattle, sheep, goats and horses are the chief animal hosts. Infections can occur from contact with contaminated carcasses, hides, wool, hair, blood, excreta, bones; and consuming uncooked, contaminate meat.  Workers in the clothing, yarn, insulation material, saddle pads and fertilizer industries are noted as reported cases of occupational anthrax. Anthrax spores have also been shown to be spread by houseflies.  Anthrax is not known to be transmitted by person-to-person contact.

Treatment of Anthrax

Anthrax is readily susceptible to numerous antibiotics. 

Table 1 Antibiotics with Activity versus Anthrax



•penicillin G

Antibiotics that have shown activity against anthrax.  The antibiotics in bold print are those most referenced for treatment of anthrax. Penicillin G has long been the drug of choice used for the treatment of anthrax.  A treatment regimen of penicillin G of 2 million units given intravenously every two hours is recommended for the treatment of inhalation anthrax.   The U.S. military favors the use of a drug combination of 400 mg of ciprofloxacin given intravenously every eight to twelve hours, given with an initial dose of 200 mg of doxycycline intravenously, followed by a dose of 100 mg of doxycycline intravenously every eight to twelve hours.

Prevention of Disease

The primary method for preventing anthrax in exposed individuals is the use of the vaccine.  This vaccine consists of anthrax bacillus that is attenuated (weakened),  unencapsulated, and nonproteolytic strain. This process allows for the immune system to recognize the bacillus as a foreign body without causing infection.  Repeated exposure to the vaccine strengthens the immune response to the bacillus over time.

First introduced in 1971 and manufactured by the Michigan Department of Public Health, the anthrax vaccine was designed for use in workers in the animal hide handling industry.  This vaccine has been adapted for use in the military as protection against exposure to anthrax spore used as a weapon.  Table 2 lists the dosing schedule for the

Table 2 Dose Schedule for Anthrax Vaccine

•Initial dose

•2 weeks
•4 weeks
•6 months
•12 months
•18 months

Vaccine. A 0.5-ml dose is given subcutaneously over this interval, providing an immunized person with immunity after one and a half years. A booster of 0.5 ml is given annually to maintain immunity.  If an individual fails to receive the annual booster, the vaccination cycle must be started again in order to maintain immunity.

There are several drawbacks to using a vaccine.  First, immunized personnel must maintain the annual schedule of booster immunizations or lose immunity.  Second, immunity to exposure to anthrax is not conferred immediately to upon the first dose, but only after an 18-month course of injections. Emergency response personnel must receive the full course of injections to confer immunity.  With rapid turnover of personnel, keeping a cadre of anthrax immunized individuals will be difficult. Third, the anthrax vaccine does not confer absolute immunity. Of all personnel immunized, 91% should have immunity to exposure to anthrax. Fourth, a vaccine will not be proof against an overwhelming exposure to anthrax spores. A vaccine acclimates the immune system to immediately recognize anthrax bacillus as a foreign body.  If the dose of anthrax spore is great enough, the immune system can be overwhelmed, overtaxing its ability to fight off the infection.  Lastly, the anthrax vaccine is approved for use by the US Food and Drug Administration for use in the prevention of cutaneous anthrax. Its efficacy in human beings to provide immunity to inhaled anthrax spores has not been proven. However, the use of this vaccine is the only current viable option to confer some immune response activity in vaccinated individuals.

Another method for providing protection against exposure to anthrax infection is to use antibiotics in preventative (prophylactic) doses. Experimental evidence in animals has indicated that antibiotic treatment one day after exposure to spore anthrax can provide protection against death.  Doses of 500 mg of ciprofloxacin and 100 mg of doxycycline given twice a day orally over the course of four weeks, with the start of anthrax vaccine can be effective.  If no vaccine is available, an increase to twelve to sixteen weeks of antibiotics is recommended.


Materials that are contaminated with anthrax bacillus or spore must be decontaminated. Spores can be destroyed by: steam under pressure (autoclave) for one hour; dry heat above 159 o C; or boiling water for 30 minutes with disinfectants. Table 3 lists chemicals that have been used as anthrax bacillus and spore disinfectants.

Table 3 Anthrax Disinfectants

•chloride solution
•peracetic acid 3%
•formaldehyde 10% in water
•potassium permanganate
•hydrogen peroxide 3%
•sodium hypochlorite 0.5%


Animals who died of anthrax infection have been traditionally either cremated or deeply buried with quicklime.

Problems of Anthrax Use as a Weapon

Anthrax release in a population center would pose a number of problems for emergency response and remediation personnel. Appropriate personal protective equipment is essential to prevent infection in responders. The Centers for Disease Control classifies working with infected animals as an Animal Biohazard 3 rating, which requires special facilities and personal protective equipment. Similar measures would be necessary to control remediator exposure to anthrax spore.

Since anthrax is persistent in the environment, contamination of soil would require special treatment. Gruinard Island, the location of the British anthrax experiments remained restricted to human entry for over fifty years.  Similar decontamination procedures would be necessary for open soil and park space contaminated with anthrax spore.

Buildings with operating fresh air intakes of the heating, ventilation and air-conditioning (HVAC) system must be assumed to be contaminated if within the estimated plume of an anthrax spore release.  All ductwork, interior rooms, air filters and related HVAC system machinery would have to be disinfected or disposed of to prevent the spread of spores.

Drug delivery logistics are also a problem with anthrax exposure. Please note that the recommended medications to combat anthrax infections are to be delivered intravenously.  Administration of these medications require trained medical personnel, IV tubes, IV fluids, IV bags and other related equipment.


Anthrax has been researched and developed as a weapon of mass destruction since World War I. The technology for growing anthrax in the laboratory and vaccination of animals is over one hundred years old. With the perceived ease of production in the laboratory, the use of anthrax by terrorists as a weapon is a viable threat. A combination of understanding of the potential threat, response, and treatment of disease would serve to contain the impact of the use of anthrax spore as a weapon.