Retroviridae

A family of RNA viruses 80-100 nm in diameter, enveloped, and containing two identical molecules of positive sense, single-stranded RNA, molecular weight 3-6 × 10⁶; genomic RNA serves as a template for the synthesis of a complementary DNA, which may be integrated into the host DNA. At present, seven genera have been identified: Mammalian type B retroviruses, Mammalian type C retroviruses, Avian type C retroviruses, Type D retroviruses, BLV-HTLV retroviruses, Lentivirus, and Spumovirus.

A family of viruses grouped in three subfamilies: Oncovirinae (HTLV-I, HTLV-II RNA tumor viruses), Spumavirinae (foamy viruses), and Lentivirinae (HIV-like viruses, visna, and related agents).