Understanding the Bioterrorist Threat: Facts and Figures

Report Homeland Security

Understanding the Bioterrorist Threat: Facts and Figures

October 11, 2001 20 min read Download Report

Authors: Jack Spencer and Michael Scardaville


The Use of Biological Weapons

Past Bioterrorist attacks

Characteristics of Selected Biological Agents

Possible Biological Agents

Potential Means of Delivery

Producers of Biological Weapons

Map: Countries Possessing Biological Weapons

Comparative Effects

Is Government Prepared

The September 11 terrorist attacks on the World Trade Center and the Pentagon made starkly clear how vulnerable Americans are to terrorism at home. But as devastating as those attacks were, the likelihood is growing that terrorists may soon decide to use biological agents as weapons to extract even higher death tolls. Evidence of this includes the startling fact that the number of criminal investigations in the United States related to the use of biological materials as weapons of mass destruction more than doubled between 1997 and 1998:

  • In 1997, 22 of the 74 criminal investigations--or 30 percent--involved biological materials.

  • In 1998, 112 of the 181 criminal investigations--or 62 percent--involved biological materials. 2

As the facts about possible biological agents and the figures about their potential effects become known, the challenges for terrorists in mounting a biological attack against America may appear daunting, but they are not impossible to meet. Biological warfare is neither new nor theoretical; it has been waged effectively, in fact, since the 14th century. 3

The most likely targets for bioterrorist attacks on America are people, crops, and livestock. Moreover, some of the agents are relatively easy to obtain: In 1996, an Ohio man was able to purchase bubonic plague cultures through the mail. 4 And there are various means of delivery. Biological agents can be spread by airborne release; by injection or direct contact; through food, pharmaceutical, and water contamination; or by animal vectors such as fleas and hair. And as recent simulated exercises in various U.S. cities have shown, the United States is still ill-prepared to respond to such attacks.

According to the Centers for Disease Control and Prevention (CDC), biological agents pose a risk to national security because they are easily disseminated; cause high mortality, which would have a major impact on public health systems; cause panic and social disruptions; and require special action and funding to increase public preparedness. 5 As the following facts and figures show, the challenges facing the Bush Administration, the new Office of Homeland Security, and Congress in responding to the growing threat of bioterrorism are immense.

The Use of Biological Weapons
Biological weapons can be produced from widely available pathogens that are manufactured for legitimate biomedical research or obtained from soil or infected animals and humans. (See Table 1.) In fact, many of the infectious diseases that are associated with biological warfare are endemic to the same countries that are most often suspected of trying to develop biological weapons. And because biological agents may be cheap and easy to obtain, any nation with a basic industry or facility such as a brewery has a de facto capability to produce biological weapons. 6

Past Bioterrorist Attacks

Did You Know?

  • In the past century, plague-infested fleas, cholera, anthrax, and biological agents such as glanders have been used or field tested by aggressor nations in times of war and hostility.

  • Offensive biological weapons programs are known to exist in a dozen countries, including Iran, Iraq, Libya, North Korea, and Syria.

  • An accident at a Soviet biological weapons facility in 1979 released a plume of anthrax that killed 66 people and livestock up to 100 kilometers downwind.

  • An airborne release of 250 pounds of anthrax spores over Washington, D.C., could cause more deaths than a 1-megaton hydrogen bomb.

  • The economic impact of an anthrax attack could range from $478 million to $26 billion for every 100,000 people affected.

  • A recent war game exercise concluded that, within three months of a terrorist attack in Oklahoma City using smallpox, over 3 million people would be infected and over 1 million would die.

Since 1346, when the Mongols catapulted corpses contaminated with plague over the walls into Kaffa (Crimea) and forced the besieged Genoans to flee, there have been many documented cases of the use of biological agents against people. 7

  • In 1767, during the French and Indian Wars, the British gave hostile Indians the blankets they had used to wrap British smallpox victims. The disease quickly spread among the Indians. 8

  • During World War I, the Germans used glanders and other microbial agents to infect draft animals herded into ports within the United States and Argentina en route to the western front. 9

  • From 1932 to 1945, Japanese forces in Manchuria experimented with plague-infected fleas, anthrax, cholera, and several other diseases to use as biological weapons. Japan conducted field trials against Chinese cities in the late 1930s. The agents were sprayed from aircraft and placed in water or food supplies, with mixed results. There were several plague outbreaks in Chinese cities. Japan reportedly has killed 1,700 of its own troops through mishaps in developing biological weapons. 10

  • The Bulgarian secret police are known for developing a means to assassinate someone by shooting a pellet enriched with ricin, a highly lethal toxin cultivated from a poisonous protein in the castor bean, from the tip of an umbrella into the victim's skin. In September 1978, the Bulgarian secret police used this method to assassinate dissident Georgi Markov in London. 11

  • In 1979, a plume of anthrax released in Sverdlovsk, Russia, killed 66 of 77 reported infected people who were downwind from the release point. Livestock 10 to 100 kilometers downwind also died. In 1992, President Boris Yeltsin admitted that the tragedy was due to an accident at a former Soviet biological weapons facility. 12

  • In 1984 in Oregon, the Rajneeshee religious cult contaminated salad bars in local restaurants with salmonella bacteria in an effort to prevent people from voting in a local election. Although no one died, 751 people were diagnosed with the food-borne illness. 13

  • In 1986, Tamil guerrillas operating in Sri Lanka poisoned tea with potassium cyanide in an effort to cripple the Sri Lankan tea export industry. 14

  • In 1993, Iran reportedly plotted to contaminate water supplies in the United States and Europe with an unspecified biological agent, and Israeli Arabs plotted to poison the water in Galilee with an "unidentified powder." 15

  • In 1994, the Aum Shinrikyo cult attempted to release anthrax from the tops of buildings in Tokyo. 16 In 1995, the cult placed three briefcases designed to spray botulinum toxin in the Tokyo subway in an attack that ultimately failed. 17

  • In 1995, two members of a Minnesota militia, the Patriots Council, were convicted of possessing ricin that they planned to use against law-enforcement officers who had served legal papers on members of the group. 18

Clearly, the threat of biological terrorism is real and growing.

Possible Biological Agents
As Table 1 shows, the menu of biological agents that could inflict massive harm on Americans is broad. The viruses, bacteria, or other toxins can be relatively easy to acquire, process, and disseminate or very difficult and unstable, with many possibilities between those extremes. The likelihood that a terrorist will use one agent over another depends on these factors as well as on how lethal the agent is and whether there is a vaccine or treatment readily available to counter its effects.

The focus on anthrax as a possible biological weapon for a terrorist attack grew significantly following the recent death from anthrax of a man in Florida and the discovery that his coworker has anthrax spores in his nostrils. Anthrax infections can occur either from inhalation of the spores or from skin contact. Inhalation anthrax is almost always fatal once the symptoms--which mimic influenza--appear.

The anthrax bacterium (Bacillus anthracis) is most prevalent in agricultural regions, where the spore occurs naturally among animals. These regions include South and Central America, Southern and Eastern Europe, Asia, Africa, the Caribbean, and the Middle East. Outbreaks occur in both wild and domestic cattle, sheep, goats, camels, antelopes, and other herbivores, but they can also occur in humans who have been exposed to infected animals or to tissue from infected animals. 19

Additional facts affecting its possible use by terrorists include the following:

  • Anthrax can be cultured from almost any soil that supports livestock. Anthrax seed stock, however, is difficult to process and disseminate with great success. 20 The minimal lethal dose for inhalation of anthrax (reportedly 5,000 to 10,000 spores) is high compared with other biological agents. 21

  • Most infections (about 95 percent) occur when the bacterium enters a cut or skin abrasion--for example, in unprotected workers handling the wool, hides, leather, or hair products (especially goat hair) of infected animals. Skin infection begins as an itchy bump resembling an insect bite; within two days, it develops into a vesicle and then a painless ulcer, usually 1-3 cm in diameter, with a characteristic black necrotic (dying) area in the center. Lymph glands in the area may swell. About 20 percent of untreated cases of infection through the skin result in death. Deaths are rare with appropriate antimicrobial therapy. 22

  • The anthrax vaccine is effective for preventing anthrax infection through the skin. It appears to be effective for some, but not all, strains of inhalation anthrax in some animal species. 23 Testing to determine the effectiveness and possible side effects of this vaccine is ongoing.

Smallpox is also mentioned frequently as a possible biological weapon. The reasons: The disease is highly infectious and associated with a high mortality rate. Little vaccine is available, and there is no effective treatment for the disease.

Currently, no one under the age of 30 has been vaccinated against smallpox. For physicians, the most difficult aspect of diagnosing the disease is a lack of familiarity with it. 24

In 1980, the World Health Organization (WHO) declared endemic smallpox eradicated, with the last occurrence in Somalia in 1977. Currently, there are only two WHO-approved and inspected repositories: the Centers for Disease Control and Prevention (CDC) in the United States and Vector Laboratories in Russia. However, clandestine stockpiles may exist.

Potential Means of Delivery

Biological agents can be spread by aerosol sprays, explosives, or the contamination of food or water supplies. 25 The effectiveness of an attack can be affected by the particle size of the agent itself, the stability of the agent under desiccating conditions, exposure to ultraviolet light, wind speed and direction, and atmospheric stability. 26

In most terrorist incidents that involved chemical or biological contamination, the method of dissemination is unknown. (See Chart 1.) In cases where the method has been identified, the terrorists have relied on airborne dissemination (17 percent); pharmaceutical contamination (16 percent); food or drink contamination (15 percent); injection or direct contact (13 percent); and water contamination (11 percent). 27

Additional facts regarding delivery of biological weapons that counterterrorism planners must consider include the following:

  • No reliable fixed means exist for detecting biological agents released into the atmosphere over large areas such as cities. 28 Biological attacks are likely to be recognized only after affected people start to become sick. In some cases, this may not occur for weeks after an attack.

  • There are various plausible scenarios for biological and chemical contamination of agricultural products (similar, for example, to the German practice in World War I). These include infecting livestock with hoof and mouth disease, pigs with African Swine Fever, chicken with the Newcastle disease virus, or crops (such as wheat, corn, rice, or soy beans) with Karnal Bunt, stem rust, or leaf rust.

  • Imported materials could be used by terrorists to introduce pathogens into a country. These include straw, animal feed, and fertilizer. Imports infected before they leave the country of origin could facilitate multiple outbreaks over large geographic areas in recipient countries, mimicking a natural event (such as the recent outbreak of hoof and mouth disease in Japanese cattle in two widely separated areas). 29

  • The greatest number of potential casualties involves the airborne release of biological and chemical agents. Releases within enclosed spaces (such as subways, buildings, domed sports arenas, airports, or train stations) require less of these agents but are likely to be quite lethal because the agent remains concentrated in the confined airspace. Such releases would require less than about 1 gram of biological agents. 30

  • Open-air release of biological and chemical weapons can affect the broadest area with the highest number of casualties. Temperature inversions, in particular, could trap these agents close to the ground, substantially increasing the level of surface doses. Rain washes most of these agents out of the air. Some biological and chemical agents may remain harmful in groundwater for a period of time; however, most become harmless. 31

  • Biological agents may be aerosolized by explosion or by use of a spray nozzle. Explosive release tends to be inefficient (according to one estimate, leaving approximately 0.1 percent to 1 percent of the agents in the 1 to 5 micron size range), with the heat and shock of the explosion destroying much of the agent. 32 Spray release is more efficient (up to 25 percent efficient for liquid slurries and up to 40 percent for dry biological agents that are ground to the proper size before dispersal). 33

  • Being indoors during an airborne attack can lessen the exposure depending on the building. The degree of exposure for people inside a closed building when a biological or chemical plume passes outside is reduced by a factor of two or more for typical American homes and by a factor of as much as 10 or more for hermetically sealed office buildings, depending on the quality of the air filters in the heating, ventilation, and air conditioning system. 34

Producers of Biological Weapons
Offensive biological weapons programs reportedly exist today in a dozen countries, particularly in the Middle East and Asia. Countries currently listed as "proliferation concerns" by the Henry L. Stimson Center, a think tank in Washington, D.C., include China, Egypt, Iran, Iraq, Israel, Libya, North Korea, Syria, and Taiwan. 35

  • China continues to maintain some elements of an offensive biological weapons program that it is believed to have started in the 1950s. It possesses biotechnology infrastructure sufficiently advanced to allow it to develop and produce biological agents. Its munitions industry is sufficient to allow it to weaponize such agents, and it has a variety of means that could be used for delivery.

    China's offensive biological warfare capability is believed to be based on technology developed before its accession in 1984 to the Biological and Toxin Weapons Convention (BWC). Since then, China has claimed that it has never researched, produced, or possessed any biological weapons and would never do so. Nevertheless, its declarations under the BWC guidelines for confidence-building purposes are believed to be inaccurate and incomplete. 36

  • India has many well-qualified scientists, numerous biological and pharmaceutical production facilities, and biocontainment facilities suitable for research and development of dangerous pathogens. At least some of these facilities are being used to support research and development for biological warfare defense work. 37

  • Iran has a growing biotechnology industry, significant pharmaceutical experience, and the overall infrastructure to support a biological warfare program. Tehran has expanded its efforts to seek considerable dual-use biotechnical materials and expertise from entities in Russia and elsewhere, ostensibly for civilian purposes. Outside assistance, which Iran needs, is difficult to prevent because of the dual-use nature of the materials and equipment it seeks and the many legitimate end uses for these items.

Iran's biological weapons program began during the Iran-Iraq war. Iran is believed to be pursuing offensive biological warfare capabilities, and its effort may have evolved beyond agent research and development to the ability to produce small quantities of agents. 38

  • Libya ratified the BWC but has continued its biological warfare program. The program has not advanced significantly beyond research and development, though it may be capable of producing small quantities of biological agents. It has been hindered by a poor scientific and technological base, equipment shortages, a lack of skilled personnel, and U.N. sanctions from 1992 to 1999.

    Without foreign assistance and technical expertise on dual-use materials, Libya's biological warfare program is not likely to make significant progress. However, with the suspension of U.N. sanctions, Libya's ability to acquire biological-related equipment and expertise will increase. 39

  • North Korea has acceded to the BWC but nonetheless has pursued biological warfare capabilities since the 1960s. Pyongyang's resources include a rudimentary (by Western standards) biotechnical infrastructure that could support the production of infectious biological warfare agents and toxins such as anthrax, cholera, and plague. North Korea is believed to possess a munitions-production infrastructure that would allow it to weaponize biological warfare agents, and it may have biological weapons available for use. 40

  • Pakistan is believed to have the resources and capabilities to support limited biological warfare research and development. It may continue to seek foreign equipment and technology to expand its biotechnical infrastructure. Pakistan has ratified the BWC and participates actively in compliance protocol negotiations. 41

  • Iraq is known to have manufactured relatively large quantities of anthrax and botulinum toxins; however, its scientists apparently have had difficulty developing efficient spray nozzles, forcing them to rely on explosive release by Scud missiles equipped with these toxins. 42 Iraq may have produced up to 10 billion doses of anthrax, botulinum toxin, and aflatoxin. 43

Under supervision by the U.N. team of inspectors (UNSCOM), 38,537 filled and unfilled munitions, 690 tons of agents, 3,000 tons of chemical precursors to chemical weapons agents, and thousands of pieces of production equipment and analytical instruments were destroyed in Iraq before UNSCOM was expelled in December 1998. Since then, no complete accounting of Iraq's chemical weapons program has been possible. 44 Moreover:

  1. Iraq had removed chemical weapons, equipment, and materials from the main site of the al-Muthanna State Establishment before the first UNSCOM inspection team arrived in June 1991; no full accounting of these materials has been forthcoming.

  2. Iraq's claims that it has destroyed 15,620 chemical munitions are unverified. It also has provided no documentation regarding 16,038 chemical munitions it claims to have discarded.

  3. UNSCOM inspectors reportedly were closing in on an Iraqi program for the production of VX, a deadly chemical agent, when the standoff between Iraq and the U.N. Security Council began in the autumn of 1997. In November 1997, the inspectors found new evidence that Iraq had obtained at least 750 tons of VX precursor chemicals. Evidence of VX production was first revealed in 1995.

Comparative Effects of Different Bioterrorist Attacks
Various government and defense-related studies on the potential effects of nuclear, chemical, or biological attacks on the United States have been conducted. Much of this information is available to the intelligence and policy communities, as well as the American public and those who would harm them.

In 1993, for example, an expert at the Office of Technology Assessment (OTA), a now-defunct arm of the U.S. Congress, released his assessment of the damage that could be caused in two scenarios based on the method of delivery.

SCENARIO #1: Agents Delivered by Missile Warheads
This scenario assumes that an agent successfully reaches U.S. soil aboard one Scud-sized warhead with a maximum payload of 1,000 kilograms. The study also assumes that the maximum use of this payload capability was not used. It is unclear whether this assumption is realistic.

The effects of such an attack by a missile loaded with a biological, chemical, or nuclear warhead can be seen in Table 2.

SCENARIO #2: Agents Delivered by One Aircraft. This scenario assumes that the agents are delivered by one aircraft carrying 1,000 kilograms (kg) of Sarin nerve gas or 100 kg of anthrax spores. It assumes the aircraft flies in a straight line over the target at optimal altitude and dispenses the agent as an aerosol. It also assumes that maximum use of this payload capability was not used. It is unclear whether this last assumption is realistic.

Table 3 shows the effects of such attacks on America.

Economic and Other Effects

Even the mere threat of a bioagricultural attack could have a devastating effect on the economy. For example, an anonymous caller to the U.S. embassy in Santiago, Chile, in 1989 claimed that Chilean grapes destined for U.S. and Japanese markets were contaminated with cyanide. The United States placed a quarantine on Chilean grapes and forced the growers to recall those that had been shipped, causing approximately $333 million in damage to the Chilean grape industry. 45

Government Estimates of the Impact
Several official reports highlight the risk posed to Americans and the effects such attacks would have on the U.S. economy.

  • The CDC has estimated that an anthrax attack by a terrorist would result in an economic impact of $477.8 million to $26.2 billion for every 100,000 persons exposed. 46

  • A 1993 OTA report estimated that 250 pounds of anthrax spores, spread efficiently over the Washington, D.C., metropolitan area, could cause up to 3 million deaths, more than from a 1-megaton hydrogen bomb. 47

  • A senior-level war game in June 2001, called "Dark Winter," looked at the national security, intergovernmental, and information challenges of a biological attack on the U.S. homeland. One conclusion of the war game, hosted by the Center for Strategic and International Studies, the Johns Hopkins Center for Civilian Biodefense Studies, the ANSER Institute for Homeland Security, and the Oklahoma National Memorial Institute for the Prevention of Terrorism: Within three months of a biological attack on Oklahoma City using smallpox, over 3 million Americans could be infected, and over a million would be killed. 48

    Moreover, the study concluded:

    an attack on the United States with biological weapons could threaten vital national security interests. Massive civilian casualties, breakdown in essential institutions, violation of democratic processes, civil disorder, loss of confidence in government and reduced US strategic flexibility abroad are among the ways a biological attack might compromise US security. 49

  • According to a U.S. Army study, a Scud missile (launched at a U.S. city from a ship lying outside U.S. territorial waters 50 carrying a warhead filled with botulinum could contaminate an area of 3,700 square km if weather conditions were ideal and an effective dispersal mechanism was available. This is 16 times greater than the reach of the same warhead filled with Sarin gas. By the time symptoms began to appear, treatment would have little chance of success; rapid field detection methods for biological warfare agents do not yet exist. 51


Jack Spencer
Jack Spencer

Senior Research Fellow for Energy and Environmental Policy

Michael Scardaville

Former Policy Analyst