Smallpox is caused by the poxvirus, which is:

Explanation

Smallpox is caused by the Variola virus, which has a double-stranded DNA genome. This type of genome allows the virus to replicate in the cytoplasm and produce complex viral particles. Other genome types, such as single-stranded DNA, double-stranded RNA, and single-stranded RNA, are found in different viruses but not in poxviruses. The double-stranded DNA structure of the Variola virus gives it stability and the ability to carry a large amount of genetic information needed for its life cycle.