Modern taxonomy of viruses of vertebrates

Abstract

The modern taxonomy of viruses of vertebrates is presented according to the information of ICTV issue 07.2019, ratification 03.2020. The leading criteria of taxonomy of viruses are named: type and structure of viral genome, mechanism of replication and morphology of virion. The periods of formation of taxonomic ranks of viruses are characterized: in 1966–1970 genera of viruses were formed, in 1971–1975 – families and subfamilies, since 1990 – orders, in 2018–2019 – realms, kingdoms, phylums, subphylums, classes, suborders, subgenеres. The nomenclature of viruses is described. Viruses belong to the Viruses domain. Viruses of vertebrates (1878 species) belong to 4 realms, 5 kingdoms, 10 phylums, 2 subphylums, 20 classes, 26 orders, 3 suborders, 45 families (of which 15 – DNA-genomic and 30 – RNA-genomic), 33 subfamilies, 345 genera and 49 subgenera. Taxonomic ranks of DNA- and RNA-genomic viruses of vertebrates are described. The DNA-genome family Anelloviridae and the unclassified RNA-genomic genus Deltavirus are not included in any realm. The family Birnaviridae is not classified within the kingdom Orthornavirae. The family of DNA-genomic Hepadnaviridae is included in the realm of RNA-containing viruses Riboviria on the grounds that the replication of hepadnaviruses occurs through the stage of RNA on the principle of reverse transcription, as in the family Retroviridae. The main taxonomic features of DNA- and RNA-genomic viruses of vertebrates are described: type and structure of viral genome (DNA or RNA, number of strands, conformation, fragmentation, polarity), shape and size of virions, presence of outer lipoprotein shell, type of capsid symmetry (spiral, iсosahedral). Some families, in addition to viruses of vertebrates, contain viruses of invertebrates and plants, in particular: families Poxviridae, Iridoviridae, Parvoviridae, Circoviridae, Smacoviridae, Genomoviridae, Rhabdoviridae, Nyamiviridae, Peribunyaviridae, Phenuiviridae, Nairoviviridae, Nodaviridae, Reoviridae and Birnaviridae – viruses of insects; families Genomoviridae, Rhabdoviridae, Phenuiviridae and Reoviridae – viruses of plants; family Nyamiviridae – viruses of nematodes, cestodes, sipunculidеs and echinoderms; family Rhabdoviridae – viruses of nematodes; family Reoviridae – Eriocheir sinensis reovirus; family Birnaviridae – viruses of tellines and rotifers.