Whats the genus/species for smallpox?

[Hades]

is it Orthopoxvirus vaccinia

[ecoli]

no, it's Orthopoxvirus variola, but there are two forms of it, major and minor.

[DrZoidberg]

As already mentioned, smallpox is the variola virus (major or minor). The vaccinia virus is closely related to cowpox and thus used to vaccinate towards smallpox giving birth to the term vaccine.