members of Group VI use virally encoded reverse transcriptase, an RNA-dependent DNA polymerase, to produce DNA from the initial virion RNA genome. This DNA is often integrated into the host genome, as in the case of retroviruses and pseudoviruses, where it is replicated and transcribed by the host. Group VI includes: Order Ortervirales Family Belpaoviridae Family Metaviridae Family Pseudoviridae Family Retroviridae – Retroviruses, e.g. HIV Family Caulimoviridae – a VII group virus family (see below) The family Retroviridae was previously divided into three subfamilies (Oncovirinae, Lentivirinae, and Spumavirinae), but are now divided into two: Orthoretrovirinae and Spumaretrovirinae. The term oncovirus is now commonly used to describe a cancer-causing virus. This family now includes the following genera: Subfamily Orthoretrovirinae: Genus Alpharetrovirus; including Avian leukosis virus and Rous sarcoma virus Genus Betaretrovirus; including Mouse mammary tumour virus Genus Gammaretrovirus; including Murine leukemia virus and Feline leukemia virus Genus Deltaretrovirus; including Bovine leukemia virus and the cancer-causing Human T-lymphotropic virus Genus Epsilonretrovirus Genus Lentivirus; including Human immunodeficiency virus 1 and Simian and Feline immunodeficiency viruses Subfamily Spumaretrovirinae: Genus Bovispumavirus Genus Equispumavirus Genus Felispumavirus Genus Prosimiispumavirus Genus Simiispumavirus Note that according to ICTV 2017, genus Spumavirus has been divided into five genera, and its former type species Simian foamy virus is now upgraded to genus Simiispumavirus with not less than 14 species, including new type species Eastern chimpanzee simian foamy virus. Group VII viruses Both families in Group VII have DNA genomes contained within the invading virus particles. The DNA genome is transcribed into both mRNA, for use as a transcript in protein synthesis, and pre-genomic RNA, for use as the template during genome replication. Virally encoded reverse transcriptase uses the pre-genomic RNA as a template for the creation of genomic DNA. Group VII includes: Family Caulimoviridae — e.g. Cauliflower mosaic virus Family Hepadnaviridae — e.g. Hepatitis B virus The latter family is closely related to the newly proposed Family Nackednaviridae — e.g. African cichlid nackednavirus (ACNDV), formerly named African cichlid hepatitis B virus (ACHBV). whilst families Belpaoviridae, Metaviridae, Pseudoviridae, Retroviridae, and Caulimoviridae constitute the order Ortervirales. Endogenous Endogenous retroviruses are not formally included in this classification system, and are broadly classified into three classes, on the basis of relatedness to exogenous genera: Class I are most similar to the gammaretroviruses Class II are most similar to the betaretroviruses and alpharetroviruses Class III are most similar to the spumaviruses. Controversy Retroviruses have been the