Here ya go (just posting the relevant section):
New Drug to Aid in Protection Against Bioterrorism. Although smallpox was eradicated in the 1970's, smallpox has re-emerged as a public health concern because of its potential use as a biowarfare agent. At present, no drugs exist to treat orthopoxviruses, the family of respiratory-transmitted viruses of which smallpox is a member. Recently, NIH-supported investigators tested the efficacy of a drug called cidofovir against these viruses. Cidofovir is currently licensed to treat an unrelated disease. The investigators, expanding upon prior findings by another research team, found that cidofovir inhibits a broad spectrum of orthopoxviruses in vitro, completely protects monkeypox-infected monkeys from signs of disease, and is highly effective in protecting and treating cowpox virus in mice. These findings suggest cidofovir may be effective treatment for smallpox infection. Martinez MJ, Bray MP,Huggins JW: A mouse model of aerosol-transmitted orthopoxviral disease. Archives of Pathological Laboratory Medicine, 124(3):362-77. 2000. Smee DF, Bailey KW, Wong M-H, Sidwell RW: Intranasal treatment of cowpox virus respiratory infections in mice with cidofovir. Antiviral Chemical Chemotherapy, 11(4):303-9. 2000.