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Smallpox (Variola virus) is considered a high-priority biological threat agent. It can be spread using an aerosol spray, transmitted from person to person via close contact, and can survive in the environment up to one day, depending on ambient conditions. The fatality rate following infection is high, and there is no effective, approved treatment. Routine smallpox vaccination ended in the U.S. in 1972. Those who received the vaccination may experience a reduction in symptom severity and a decreased mortality rate, however, the infection rate and spread of disease amongst the general population is expected to be high.

On September 23, 2004, the Secretary of Homeland Security determined that the smallpox virus is a material threat to the U.S. population sufficient to affect national security. Because the threat is credible and smallpox has the potential to cause significant casualties and massive disruption of political, economic, and social infrastructures in the U.S., strong efforts to reduce U.S. vulnerability to smallpox are warranted. As such, BARDA is supporting the development of both vaccines and antivirals that can protect against or treat smallpox. An effective antiviral treatment could mitigate the effects of smallpox disease. It is likely that such an antiviral may also be effective against other pox viruses.

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