FEATURE ARTICLE
The Growing Threat of Biological Weapons
The terrorist threat is very real, and it's about to get worse. Scientists should concern themselves before it's too late
Steven Block
The Plague and Anthrax
Biological warfare is not a new phenomenon. The ancient Romans, and
others before them, threw carrion into wells to poison their
adversaries' drinking water. In the 14th century the Tatars
catapulted the bodies of bubonic-plague victims over the city walls
of Kaffa, a Black Sea port that served as a gateway to the Silk Road
trade route. People inside the city soon came down with the disease,
suggesting that the maneuver may have worked—but the tactic
may have exceeded the Tatars' operational goals. Some of the city's
inhabitants escaped in sailing ships, which happened to be infested
with rats, carrying fleas infected with the causative agent of
plague, the bacterium Yersinia pestis. The escaping ships
entered various Italian ports that subsequently served as foci for
the spread of the disease. Over the next three years, the bubonic
plague—the Black Death—raged northward, wiping out
nearly a third of Western Europe.
It was not until the 19th century that the microbial basis for
infectious disease was understood. One of the first illnesses to be
explained by the new germ theory was anthrax, an infectious disease
common to sheep and cattle. Indeed, the primary architects of the
germ theory??Robert Koch, Louis Pasteur and Joseph Lister??were
instrumental in describing anthrax and its containment. Koch was the
first to isolate and describe the anthrax bacterium (Bacillus
anthracis). Pasteur developed the first animal vaccine against
anthrax, which, together with Lister's ideas about antiseptic
precautions, helped turn the tide against outbreaks of the disease.
Anthrax is only weakly communicable in humans and rarely causes
disease, unless the bacterium comes into contact with the
bloodstream through a wound (causing cutaneous anthrax) or is
ingested in contaminated meat (resulting in intestinal anthrax).
However, Bacillus anthracis has the ability to form
resistant spores, which can remain viable for over a hundred years
if kept desiccated and out of direct sunlight. Breathing in
significant numbers of spores (typically estimated at about 10,000)
can lead to inhalation anthrax in humans, which was historically
called "woolsorter's disease" because spores were
prevalent in the contaminated wool of sheep in 19th-century England.
Inhalation anthrax is a very deadly disease in humans. Unless
treated with large doses of a penicillin-type antibiotic within the
first day or so of exposure it has a mortality rate in excess of 80
percent. This is to be contrasted with smallpox, which has a
mortality rate of "only" around 30 percent. Only some
filoviruses, such as Ebola, which cause hemorrhagic fevers, have
comparable rates of mortality.
All of this suggests why Bacillus anthracis became the
agent of choice for most biological warfare programs. Consider the
properties of anthrax. It is convenient: Variants of the anthrax
bacterium can be isolated worldwide (although not all possess equal
virulence), and great quantities of spores can be readily prepared
from liquid cultures. It is robust: Once desiccated and stabilized,
hardy spores have a long shelf life and are well suited to
weaponization in a device that can deliver a widespread aerosol. It
is self-terminating: Airborne spores remain infectious until they
fall to the ground, where most become inactivated by sunlight. It is
effective: After inhalation the spores produce disease with a high
mortality and morbidity. It can be contained: Anthrax is not very
communicable, thereby reducing the risk that it will spread beyond
the intended target. Moreover, a well-established vaccine exists
that can prevent the onset of the disease, allowing it to be used
safely by the aggressor. This is a two-edged sword, of course, since
the vaccine may be available to the target population as well. For
this reason alone, anthrax doesn't quite qualify as the perfect bioweapon.
There are certain other drawbacks to anthrax as a weapon. The number
of spores that must be delivered to the lungs to produce the disease
is quite high compared with some other infectious agents??it has
been estimated that certain viruses and rickettsiae may communicate
disease with just a single particle. Finally, for conventional
anthrax, antibiotic treatment can be effective if administered
quickly. Even so, of all the natural biowarfare agents, anthrax
traditionally ranks near the top of everyone's short list.
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