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What Is Smallpox?

Smallpox is a disease caused by a poxvirus that is transmitted from person to person that causes high fever, characteristic rash, and may kill about one-third of those infected. Smallpox (also called variola) is the only disease that has been completely wiped out throughout the world. Smallpox is also potentially one of the most devastating biological weapons ever conceived.

Due to the success of an intense worldwide public health initiative, not one documented naturally occurring case of this highly infectious, deadly disease has occurred since Oct. 26, 1977. (An unvaccinated hospital cook in Somalia was the last person to naturally contract smallpox.) The World Health Organization (WHO) officially declared smallpox eradicated in 1980.

At that time, all remaining collected supplies of the smallpox virus were supposed to be destroyed or sequestered in two laboratories, one in the United States and one in Russia. Geopolitical events in the last decade and revelations concerning offensive biological warfare programs by certain foreign governments have raised concern that this virus may have fallen into the hands of other foreign states who might seek to use the virus as a biological weapon.

  • History of smallpox: For centuries, smallpox affected political and social agendas. Evidence of smallpox infection has been found in Egyptian mummies. Smallpox epidemics plagued Europe and Asia until 1796, when Edward Jenner tested his theory of disease protection. He did this by inoculating a young boy with material obtained from a milkmaid who was infected with the milder cowpox virus. The success of that experiment led to the development of a vaccine (from vacca, the Latin word for cow). Afterward, the incidence of smallpox infection in Europe steadily declined.
    • In the Americas, smallpox severely weakened the native population. They had never been exposed to smallpox, which the European explorers brought with them to the Americas in the 1600s. The British forces at Fort Pitt (later to become Pittsburgh, Pa.) purposefully gave smallpox-contaminated blankets and goods to Native Americans during the French and Indian Wars in an attempt to weaken the Native American resistance to colonial expansion. Due to this and through natural spread, the epidemic that followed killed half of the Native American population.
    • Once the disease and its method of spread were understood more thoroughly, smallpox vaccination became mandatory in developed countries in the early 1900s. The development of the vaccinia virus, coupled with aggressive immunization, led to the eventual control and eradication of smallpox in 1977.
    • Since the last documented "naturally occurring" case in 1977, only two deaths from smallpox have been reported (1978 in Birmingham, England). Both deaths were the result of laboratory accidents.
  • Current locations of smallpox virus: Only two laboratories in the world are known to house smallpox virus: the Centers for Disease Control and Prevention (CDC) in Atlanta, Ga., and the State Research Center of Virology and Biotechnology in Koltsovo, Russia.
    • Various sources from the Soviet Union allege the Russian military had pursued and currently pursues an active biological warfare program. In 1992, Russian President Boris Yeltsin confirmed a suspected outbreak from an accidental release of aerosolized anthrax (anthrax stored in a container that allows it to be released into the air) near a military microbiology laboratory in 1979.
    • Dr. Ken Alibek, a former senior microbiologist in the Russian Offensive Biological Weapons Program, has alleged that, in 1980, the Soviet Union started large-scale production of the smallpox virus and genetic recombination of more potent strains. Since the fall of the Soviet Union, concern exists that this knowledge may be used in other countries. The extent of smallpox stockpiles in other countries is unknown but may have become substantial since the collapse of the Soviet Union.
    • The consequences of a smallpox outbreak can only be estimated. About 30% of unprotected people who are exposed to a person with smallpox would themselves become infected. Of these, 30% would probably die from infection. Diagnosis is difficult during early stages of the disease. Presently, insufficient supplies of vaccine exist to ensure eradication of smallpox in case the disease is released intentionally in a large-scale attack.
  • Are previous vaccinations still protective? Routine vaccination of the general population in the United States stopped after 1980. Vaccination of military personnel was discontinued in 1989. Researchers estimate that vaccinated people retain immunity for about 10 years, although the duration has never been fully evaluated. Therefore, the current population in the United States is considered vulnerable to smallpox. Almost half of the U.S. population is younger than 30 years of age and has never been vaccinated.
    • The ease of production and aerosolization of the virus is well documented. Researchers estimate that only 10-100 virus particles are necessary to infect someone. Thus, weaponized smallpox is a potential biological weapon of staggering danger.
Medically Reviewed by a Doctor on 10/24/2016

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Smallpox and Biological Warfare

Variola represents a significant threat as a biological warfare agent. Variola is highly infectious and is associated with a high death rate and secondary spread. Currently, the majority of the U.S. population has no immunity, vaccine is in short supply, and no effective treatment exists for the disease. Two WHO-approved and inspected repositories remain: One is at the Centers for Disease Control and Prevention in the United States and the other at Vector Laboratories in Russia. It is widely believed that clandestine stockpiles exist in other countries such as Iraq and North Korea.

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Smallpox »

Smallpox is an acute contagious disease caused by the variola virus (Poxvirus variolae), a member of the Poxviridae family of the genus Orthopoxvirus.

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