BetaretrovirusBetaretrovirus is a genus of viruses in the family Retroviridae.Example of viruses in the genus include: Mouse mammary tumor virus, enzootic nasal tumor virus, and simian retrovirus types 1, 2 and 3.TaxonomyThe genus contains the following species, listed by scientific name and followed by the exemplar virus of the species:Betaretrovirus lan, Langur virusBetaretrovirus maspfimon, Mason-Pfizer monkey virusBetaretrovirus murmamtum, Mouse mammary tumor virusBetaretrovirus ovijaa, Jaagsiekte sheep retrovirusBetaretrovirus squmon, Squirrel monkey retrovirus