Smallpox as a biological weapon

DEFINITION: Contagious viral disease characterized by high fever and a pustular rash that may cover the body.

SIGNIFICANCE: Given the severity of certain forms of smallpox and the present-day lack of immunity to it among the world’s population, the disease has the potential to be used as a weapon for mass devastation.

Smallpox is caused by a viral agent, a member of a family known as the poxviruses. Other viruses in the family include a variety of agents with the surname “pox” (monkeypox, cowpox) and vaccinia, but smallpox is the only one that naturally infects humans and has the potential of causing the deaths of a significant number of its victims. The virus is highly transmissible through contact with infected persons, both through oral secretions and through objects contaminated with the virus.

History of Smallpox

Smallpox is among the most ancient of human diseases, dating back at least to the times of the pharoahs in twelfth century BCE Egypt. Likewise, the disease was prevalent in Southeast Asia and China during this era. The first written description of a disease that was likely smallpox is found in the fourth century C.E., in the writings of Eusebius of Caesarea; the first recorded epidemic of the disease in the Middle East came a century later. Common in Europe by the sixteenth century, smallpox was transported to the Americas by Spanish explorer Hernán Cortéz (c. 1520); it wreaked havoc there on the native populations and opened the way for Spanish conquest.

Although the cause of smallpox was unknown in the eighteenth century, it was clear even to the casual observer that the illness was devastating to populations that had never been previously exposed; mortality could approach levels as high as 90 percent among such peoples. In Europe, where the disease had by then been known for centuries, mortality still remained at a level of 20–30 percent in the most severe outbreaks. Survivors generally exhibited severe scarring at the sites of “pocks” that had covered the body.

Two forms of the disease were apparent. The more severe type, referred to above, was known as Variola major. A less severe type, Variola minor, exhibited a much lower mortality rate, as low as 1–2 percent. The basis for the difference between the two forms remains unknown, as scientists have been unable to find much to distinguish the viruses associated with the two forms.

Evidence that the disease could be prevented originated with the Chinese, who, sometime around the eleventh century CE carried out a practice called variolation, in which smallpox crusts prepared as powders were inhaled or swallowed. The procedure was not always successful, but in many cases it did provide a measure of protection against the disease.

The practice of variolation spread through Persia (present-day Iran) and across the Middle East and Eastern Europe with the growing Muslim empire. Mary Wortley Montagu, wife of the British ambassador to Turkey and herself disfigured by the disease, had her son variolated in 1718. The practice, brought back to London with her return, was eventually described in writings that became part of the proceedings of the Royal Society of London for the Improvement of Natural Knowledge. These proceedings were read in Boston by the American physician Zabdiel Boylston as well as by the Reverend Cotton Mather, and variolation made its way into North America.

Variolation became a widespread practice in Western Europe during the eighteenth century, as published reports provided for the efficacy of the procedure and physicians from the Continent traveled to London and learned of the practice. Although it never became completely safe, variolation was increasingly accepted as a means of protecting people from the devastation of smallpox.

Smallpox and Biological Warfare

Evidence for the intentional use of smallpox as a is mainly anecdotal. The earliest example may have been the introduction of the disease among Native American populations during the French and Indian War (1754–63). Devastation of the Aztecs by smallpox during Spain’s sixteenth century conquest was likely the result of accidental infection (although it clearly benefited the conquerors), but it clearly demonstrated the lack of resistance within isolated populations. The disease had appeared periodically in other native populations, creating a fear among these peoples similar to their fear of European weapons.

The French in North America were cognizant of the effects of smallpox among their Native American enemies, and at least one leader, Charles le Moyne de Longueuil, suggested its use as a weapon in the 1750s. During the French and Indian War in North America, the Americans and their British allies had mixed success in fighting Native American warriors who were often allied with the French. In 1763, British commander Sir Jeffrey Amherst reportedly approved providing native tribes with blankets that had been contaminated with the smallpox agent. Whether the blankets were ever actually distributed is unknown, but the following year some of the tribes experienced a smallpox epidemic.

Despite the use of variolation, smallpox remained common in North America in the decades that followed. The beginning of the American Revolutionary War in 1775 provided another opportunity for smallpox to have an effect on the ability of armies to fight. The British army, with its common soldiers representing the lower echelons of English society, was largely immune to the disease, either through required variolation or natural exposure, whereas the Americans were largely susceptible. An outbreak of the disease among American troops who invaded Canada was significant in eliminating the Americans as an effective fighting force. Certainly the Americans’ sheer fatigue and lack of training, as well as weather conditions, played their roles, but illness was an important element in reducing the numbers of American troops.

General George Washington several times had to decide whether to require variolation of his men. Smallpox was clearly deadly, but the side effects of variolation could include not only temporary incapacitation but also development of actual smallpox, and from there the disease could spread to others. No evidence exists that the British intentionally practiced biological warfare on the Americans, but military decisions throughout the war were often affected by either the presence or the fear of smallpox. Variolation had been banned in several of the American colonies prior to the revolution, largely because of fears that the practice could cause outbreaks of the disease; Washington reversed the ban and required the inoculation of his troops during the war to protect them against a disease to which his opponents were already immune. In particular, inoculation of the Americans during the Siege of Boston in 1775 may have played an important role in maintaining Washington’s army as a fighting force.

Smallpox remained a problem in North America, and not only in the northeastern region. In the years after the American victory over the British at Yorktown in 1781, smallpox repeatedly spread from Central America into what is now Texas and the American Southwest, frequently devastating Native American tribes. The precise numbers of deaths are unknown, but the elimination of thousands of natives and their villages certainly played a role later in the ability of colonists to subdue those populations.

Eradication of Smallpox

Variolation was a useful tool for fighting smallpox, but it was far from safe. During the 1790s, the British country physician Edward Jenner began to test a new procedure, the use of material from a bovine form of the pox, cowpox, as a means to immunize persons against smallpox. Although Jenner has been given proper acknowledgment for the thorough testing and publicizing of the practice that became known as vaccination (from the Latin word for cow, vacca), his work was not unprecedented. As early as the 1770s, Jenner was informed of the protection associated with cowpox by English dairymaids who had developed lesions as a result of milking cows that had the infection on their udders. Jenner first tested the efficacy of vaccination on himself and his family, and then on local children—with the approval of their parents. He found that vaccination with material prepared from the pustules of cowpox provided effective immunization against smallpox. Although the subsequent widespread use of the practice revealed some small degree of danger from side effects, vaccination was far superior to variolation.

Jenner had his opponents, and vaccination was far from universally accepted. It became clear, however, that the incidence of smallpox was significantly reduced in populations that had been extensively vaccinated. Eventually, compulsory vaccination became the rule, not only in England but also in the Americas. By the 1940s, smallpox had largely disappeared from most of Europe and North America. The disruption of World War II slowed many nations’ abilities to control the disease, but in the years following the war, eradication of smallpox became a goal of the newly created World Health Organization (WHO).

Unlike many viral diseases, smallpox in its “natural state” is found only in humans. The lack of any animal reservoir meant that with interruption of the spread of infection in the human population there was hope for actual elimination of the disease. In 1948, the WHO began a program aimed at eradication of the disease, the goal being to immunize anyone who had come into contact with a smallpox victim rather than relying on “simple” mass inoculation. The principle behind the decision was to prevent the spread of the illness beyond the focus of infection, thus breaking the chain and eliminating the local outbreak.

The final push to eradicate smallpox began in 1967; that year, 131,000 cases of the disease were reported worldwide. Over the next ten years, the numbers of reported cases continued to fall, and the last natural case of the disease was diagnosed in Somalia in October 1977. Other than a single accidental infection owing to a laboratory accident in 1978, no cases of smallpox have occurred in the world since then, indicating the first eradication of a human disease.

As per an agreement from 1984, the United States and Russia (then the Soviet Union) were in possession of the only two samples of smallpox in the world. The United States stored its samples at the Centers for Disease Control and Prevention laboratories in Atlanta, Georgia. Russia stored its samples at a government laboratory in Siberia. The samples were meant to be used for research purposes only, and only with specific authorization from the World Health Organization.

With the elimination of smallpox, vaccination against the disease is no longer routinely practiced, and many among the world’s population may very well lack any natural immunity to the disease. Although the smallpox virus is no longer available in the general population, viral stocks remain in laboratories in both the United States and Russia. No stores of smallpox virus are believed to be located anywhere else, but with increased attention to the possibility of terrorist threats, fears have grown that persons with malicious intent could somehow obtain samples from the existing stocks to create their own form of biological weapon.

The question of whether the smallpox viral stocks should be destroyed has been much debated and remains unresolved. Proponents of destruction argue that with the absence of widespread immunity, even an accidental infection started by a careless researcher could unleash the virus into a “virgin” population, with results that might be comparable to those experienced by Native Americans in earlier centuries. Opponents of stock elimination argue that further research on the (deoxyribonucleic acid) of the virus may shed light on the mechanism by which the virus causes disease, perhaps even leading to the production of a safer means of vaccination.

Bibliography

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