Classification and Genome
XMRV belongs to the virus family Retroviridae and the genus gammaretrovirus. It has a single-stranded RNA genome that replicates through a DNA intermediate. Its name refers to its close relationship with the murine leukemia viruses ("MuLVs"). The genome, approximately 8100 nucleotides in length, is 95% identical with several endogenous retroviruses of mice, and is 93-94% identical with several exogenous mouse viruses.
Several XMRV genomic sequences have been published to date. These sequences are almost identical, an unusual finding as retroviruses replicate their genomes with relatively low fidelity, leading to divergent viral sequences in a single host organism. The results of phylogenetic analyses of XMRV and related murine retroviruses led a group of researchers to conclude that XMRV "might not be a genuine human pathogen".
Read more about this topic: Xenotropic Murine Leukemia Virus-related Virus