Betaretrovirus
Betaretrovirus is a genus of the Retroviridae family. It has type B or type D morphology. The type B is common for a few exogenous, vertically transmitted and endogenous viruses of mice; some primate and sheep viruses are the type D.
Examples are Mouse mammary tumor virus, enzootic nasal tumor virus, and simian retrovirus types 1, 2 and 3.
