Virus Taxonomy

Classification and Nomenclature of Viruses

Online (10th) Report of the  International Committee on Taxonomy of Viruses

Editors: Elliot J. Lefkowitz, Andrew J. Davison, Sead Sabanadzovic, Stuart G. Siddell, and Peter Simmonds

Managing Editor: Donald B. Smith; Technical Editor: Richard J. Orton

Associate Editors: Balázs Harrach, Nick J. Knowles, Andrew M. Kropinski, Jens H. Kuhn, Max L. Nibert, F. Murilo Zerbini

Technical Development (web site and database): Donald Dempsey, R. Curtis Hendrickson

Copyright © 2017 International Committee on Taxonomy of Viruses
Unless otherwise noted, this work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License

Introduction to Virus Taxonomy

The first internationally organized attempts to introduce order into the bewildering variety of viruses took place at the International Congress of Microbiology held in Moscow in 1966. A committee was created, later called the International Committee on Taxonomy of Viruses (ICTV), and was given the task of developing a single, universal taxonomic scheme for all the viruses infecting animals (vertebrates, invertebrates and protozoa), plants (higher plants and algae), fungi, bacteria and archaea. The ICTV was created as a committee of the Virology Division of the International Union of Microbiological Societies (IUMS) and is governed by Statutes approved by the Virology Division. The Statutes, available from this link define the objectives of ICTV: (i) to develop an internationally agreed taxonomy for viruses (the term “viruses” for this purpose is taken to include viroids and some important groups of satellite viruses); (ii) to develop internationally agreed names for these taxa; (iii) to communicate taxonomic decisions to the international community of virologists; and (iv) to maintain an index of virus names. The Statutes also state that classification and nomenclature of viruses will be subject to rules set out in an International Code that is available from this link.

Virus taxonomy differs from other types of biological classification because the ICTV not only regulates a Code of Nomenclature but also considers and approves the creation of virus taxa (currently orders, families, subfamilies, genera and species). Priority of publication is not the determining factor. Species names are usually derived from the common (vernacular) name of the virus (usually in English) used to establish the species. The names of all recognized taxa are written in italics with an initial capital letter.

The working of the ICTV

To date, the Executive Committee (EC) has established 98 international Study Groups (SGs) covering all major virus orders, families and genera. The Chair of each SG is appointed by the relevant Subcommittee Chair, who is a member of the EC. Each subcommittee is responsible for classes of viruses with different genome configurations infecting different hosts. The current subcommittees encompass Animal DNA Viruses and Retroviruses, Animal dsRNA and ssRNA- Viruses, Animal ssRNA+ Viruses, Bacterial and Archaeal Viruses, Fungal and Protist Viruses, and Plant Viruses. SG Chairs are responsible for (i) organizing discussions among SG members of emerging taxonomic issues in their field, (ii) overseeing the submission of proposals for new taxonomy, and (iii) preparing or revising relevant chapter(s) in ICTV Reports.

Developing new taxonomy

The ICTV welcomes taxonomic proposals from any interested individual,l although in practice most are prepared by the relevant SG. An all-purpose template and guidance notes are available for downloading from https://talk.ictvonline.org/files/taxonomy-proposal-templates/. Proposals will be forwarded to all relevant SGs and will also be made available on the website for public comment. Authors are then invited to respond to any comments made. Subcommittee Chairs then present taxonomic proposals to the EC for discussion and approval at the annual EC meeting. Straightforward proposals, such as those to create new species within existing genera for which species demarcation have been previously established, can normally be approved at a single meeting. More complex or controversial proposals are made available on the ICTV website for public comment for a further year before being re-considered by the EC.

Proposals approved by the EC do not become accepted taxonomy until they have been ratified by the full ICTV membership. As specified in the Statutes, this includes members of the various Subcommittees (mostly SG Chairs), National Members and Life Members. Lists of members are provided at https://talk.ictvonline.org/information/. Ratification proceeds by an email vote, after which the approved taxonomy is updated at https://talk.ictvonline.org/taxonomy/. In general, new taxonomy approved by the EC in the summer, is ratified by ICTV Members in March-April of the next year, at which time it becomes official. This site should always be consulted for the most up-to-date ICTV taxonomic information. Summaries of the voting decisions are also prepared and published annually in an article in Archives of Virology within the  Virology Division News section.