Smallpox Biological Warfare

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Smallpox, a disease caused by variola virus, is considered one of the biggest killers in terms of diseases in human history. Its eradication culminated a decade-long World Health Organization effort which began despite serious doubt and skepticism and succeeded to bypass a plethora of obstacles occasioned by floods, famine, civil war and bureaucratic inertia.

Nevertheless, recent world events have raised concerns that smallpox could fall into the hands of questionable individuals or groups who might attempt to use the virus as a weapon. Publications from the Centers for Disease Control and Prevention reveal that the threat of smallpox being deliberately released by bioterrorists groups is presently considered as a possibility.

American and Soviet warfare programs

If we dive into the history, we can see that the United States Army began germ warfare research in 1942 as a response to intelligence about similar programs in Berlin and Tokyo. In 1956, the US government found out about existence of the Soviet bioweapons program, which resulted in the shift of emphasis from bacterial to viral pathogens.

In 1969, presiding president of the United States Richard Nixon ended America’s biological warfare program. His administration led the world in advocating the first multilateral disarmament treaty in 1972, which banned possession of such agents except for research into vaccines and treatments.

But when the World Health Organization (WHO) declared a global eradication of smallpox in 1980, Soviet officials recognized the potential of this agent as an exceptional biological weapon. The American government was unaware of the tremendous scale on which the Soviet government pursued its bioweapons operations until October 1989.

Hence US warfare projects began once again 10 years after the Soviet Union’s and on a much smaller scale. At its peak production level, the Soviet Union annually produced 100 metric tons of variola virus, whereas the United States never mass-produced this virus (or any other biological agent for that matter).

Smallpox as a potential bioweapon

Bioterrorism can be defined as a terrorist action involving the intentional release or dissemination of a biological warfare agent. Variola virus represents a high-priority, category-A agent that poses a global security risk for several reasons: facilitated transmission from person to person, high mortality rates, potential for a major public health impact, as well as potential to cause public panic and social disruption.

Smallpox is often considered the most dangerous bioterrorist weapon because of its infectivity in aerosol form and high case fatality of 30%. In addition, the world’s population has become increasingly susceptible to smallpox due to the discontinuation of vaccination, which means that only approximately 20% of the population is currently protected.

As long as stockpiles of variola virus exist, an attack is conceivable. Many fear that the retention of variola stocks by the United States and Russia puts the world in danger of a smallpox attack, and Iraq and North Korea may also have this virus in their laboratories. Furthermore, terrorists with access to modern virology equipment might genetically modify smallpox to enhance its pathogenicity even further.

Therefore an outbreak of smallpox as a result of bioterrorism should be controlled through surveillance, containment, vaccination, and isolation of cases – akin to the strategy employed to eradicate the disease in the first place. Pre-exposure vaccination would be recommended for hospital personnel likely to be exposed to smallpox while caring for patients.

In conclusion, despite the promise of variola virus’s extinction as a biological entity, the outlook of clandestine weaponization of smallpox remains worrisome, and vaccination of military personnel could be seen as a defensive stance implying willingness to use variola virus as a weapon.


  6. Lane JM, Summer L. Smallpox as a Weapon for Bioterrorism. In: Fong IW, Alibek K. Bioterrorism and Infectious Agents: A New Dilemma for the 21st Century. Springer Science & Business Media, 2010; pp. 147-167.

Further Reading

Last Updated: Aug 23, 2018

Dr. Tomislav Meštrović

Written by

Dr. Tomislav Meštrović

Dr. Tomislav Meštrović is a medical doctor (MD) with a Ph.D. in biomedical and health sciences, specialist in the field of clinical microbiology, and an Assistant Professor at Croatia's youngest university - University North. In addition to his interest in clinical, research and lecturing activities, his immense passion for medical writing and scientific communication goes back to his student days. He enjoys contributing back to the community. In his spare time, Tomislav is a movie buff and an avid traveler.


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