Virus taxonomy and the role of the International Committee on Taxonomy of Viruses (ICTV)

Abstract

The taxonomy of viruses is developed and overseen by the International Committee on Taxonomy of Viruses (ICTV), which scrutinizes, approves and ratifies taxonomic proposals, and maintains a list of virus taxa with approved names (https://ictv.global). The ICTV has approximately 180 members who vote by simple majority. Taxon-specific Study Groups established by the ICTV have a combined membership of over 600 scientists from the wider virology community; they provide comprehensive expertise across the range of known viruses and are major contributors to the creation and evaluation of taxonomic proposals. Proposals can be submitted by anyone and will be considered by the ICTV irrespective of Study Group support. Thus, virus taxonomy is developed from within the virology community and realized by a democratic decision-making process. The ICTV upholds the distinction between a virus or replicating genetic element as a physical entity and the taxon category to which it is assigned. This is reflected by the nomenclature of the virus species taxon, which is now mandated by the ICTV to be in a binomial format (genus + species epithet) and is typographically distinct from the names of viruses. Classification of viruses below the rank of species (such as, genotypes or strains) is not within the remit of the ICTV. This article, authored by the ICTV Executive Committee, explains the principles of virus taxonomy and the organization, function, processes and resources of the ICTV, with the aim of encouraging greater understanding and interaction among the wider virology community.

Four Novel Caudoviricetes Bacteriophages Isolated from Baltic Sea Water Infect Colonizers of Aurelia aurita

“…The morphological classification scheme was initially proposed by the International Committee on Taxonomy of Viruses (ICTV) which provided a framework for organizing phages into different families, genera, and species. However, with the advent of molecular biology techniques and the availability of whole-genome sequencing, the focus of phage taxonomy has shifted towards genetic and genomic information [ 7 ]. Genomic data, sequence similarities, and phylogenetic analyses assign phages to different taxonomic ranks, including families, subfamilies, genera, and species [ 8 ].…”

Discovery of novel RNA viruses through analysis of fungi-associated next-generation sequencing data

“…Identifying and rectifying incorrect classifications when new information becomes available is an ongoing and inevitable process in today's rapidly expanding field of virology. For instance, in 1975, members of the genera Rubivirus and Alphavirus were initially grouped under the family Togaviridae ; however, in 2019, Rubivirus was reclassified into the family Matonaviridae due to recognized differences in transmission modes and virion structures [ 90 ]. Additionally, the conflicts between certain members of the genera Magoulivirus and Gammapartitivirus mentioned here and their current demarcation criteria (e.g., amino acid identity, nucleotide length thresholds) need to be reconsidered.…”

From viral democratic genomes to viral wild bunch of quasispecies

“…Even today, viral species are not precisely definable unless we create an artifact that we know will have difficulty standing the test of time given the amplification of virus analyses and the tremendous increase in sequencing data. The intra‐host genetic diversity and quasispecies have not been incorporated in the current virus taxonomy, in which the species rank is the only one that is not associated with a secondary rank, as no consensus has been reached regarding the “subspecies” definition 16,27–29 . Moreover, our current ability to understand the importance of recombination between viruses, and between viruses and their hosts, leads to a much more complex view of the nature of viruses.…”