Final answer:
The smallpox virus has a double-stranded DNA genome and is known for its notable brick-shaped virions, and the WHO declared its eradication in 1980.
Step-by-step explanation:
The characteristics described in the question are indicative of the smallpox virus, which belongs to the Poxviridae family. This virus possesses a double-stranded DNA (dsDNA) genome, and its virions exhibit a distinctive oval or brick-shaped morphology ranging from 200 to 400 nm in length. It is also noteworthy for being the first virus to have been eradicated by human efforts, with the WHO declaring its eradication in 1980 after a successful global vaccination campaign.