New perspectives in virus taxonomy

Virus taxonomy is a dynamic discipline, which is subjected to continuous changes for allocating and managing new information about viruses. Traditionally, viruses used to be classified based on a variety of characters that include biological and molecular features. However, with the increasing importance of next generation sequencing (metagenomics), genetic characteristics like DNA, RNA and protein sequences, are becoming predominant over biological traits for the identification of novel viruses. Nevertheless, whether the metagenomic approach will ultimately be retained as sufficient by itself for assigning the rank of species to newly reported sequences is still unclear. Currently, virus species are grouped into genera, families and orders. The increasing divergence between taxa has prompted the International Committee on the Taxonomy of Viruses (ICTV) to expand the standing four-rank taxonomy structure (species-genus-family-order) to a virus classification including 15 ranks, up to the ""realm"" rank. Consequently, virus diversity will be addressed with a stepwise approach, first defining the species as the basal (i.e. lowest) rank then, when feasible, establishing higher ranks, by taking into consideration characters like protein structure, type and polarity of nucleic acid, etc. In addition, a standardized Linnean-style, binomial species naming format is under study, which would follow the format used in the taxonomy of other biological entities.