What are biological weapons?

Biological weapons include bacteria, viruses, and toxins that are spread deliberately in air, food, or water to cause disease or death to humans, animals, or plants. Bacteria and viruses work by entering the body, multiplying, and then overcoming the immune system. Examples include Bacillus anthracis, Yersinia pestis (which causes plague), and Variola major (smallpox). Biotoxins are the poisons given off by living entities, such as botulinum toxin, produced by the bacterium Clostridium botulinum, and ricin, which can be isolated from castor oil seeds. According to Plague Wars, Tom Mangold and Jeff Goldberg's history of biological warfare [see To Probe Further], Western counterproliferation agencies recognize 23 bacteria, 43 viruses, and 14 toxins as potential threats.

A few grams of a dried bioagent such as anthrax could infect thousands of people. Symptoms of infection would follow within a week and deaths in the days thereafter. Certain biological weapons could also cause destabilizing epidemics. Smallpox, for example, can be easily transmitted from one infected individual to another. Anthrax, in contrast, is deadly when inhaled but is noncommunicable.

In the past, only naturally occurring organisms and toxins were considered real threats. Recent advances in genetic engineering, though, have paved the way to designer bioagents. Scientists practicing such "black biology" have already created drug-resistant strains of anthrax, plague, and tularemia (a highly infectious disease that causes skin ulcers and pneumonia). Biowarfare agents could also be bred to be far more virulent and long-lived.

To an aggressor, the appeal of such weapons is that they attack populations, leaving infrastructure intact; they are effective in very small amounts; they can be produced at low cost in a short period of time; and protection and detection are difficult.

In wargames of a fictional attack on Oklahoma City, it was predicted that an infectious agent such as smallpox could spread to three million people throughout the continental United States within 12 weeks of an attack. Thankfully, the world has yet to see such a full-blown assault. But for the reasons above, there is increasing concern that bioweapons will become the preferred weapon of mass destruction.

To be sure, fabricating devices to disperse biological agents is not trivial. Typically, one needs to create an aerosol cloud containing just the right particle size—1­5 µm is the most lethal when inhaled. What's more, some agents are quite fragile and die quickly in sunlight; others, though, are more robust. Efforts in the former Soviet Union and Iraq succeeded in generating vast quantities of plague and anthrax agents, as well as the means to deliver them—by aircraft equipped with spray tanks, cluster bombs, and missiles with multiple warheads.

In short, it is far easier to make a biological weapon than to create an effective system of defense.