Monkeypox virus (MPV) is a double-stranded DNA, zoonotic virus and a species of the genus Orthopoxvirus in the family Poxviridae. It is one of the human orthopoxviruses that includes variola (VARV), cowpox (CPX), and vaccinia (VACV) viruses. But it is not a direct ancestor to, nor a direct descendant of, the variola virus which causes smallpox. Monkeypox virus causes a disease that is similar to smallpox, but with a milder rash and lower death rate. Variation in virulence of the virus has been observed in isolates from Central Africa where strains are more virulent than those from Western Africa.