International Committee on Taxonomy of Viruses

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International Committee on Taxonomy of Viruses
Formation1966;56 years ago (1966)
PurposeRegulation of taxonomy of viruses
Fields Taxonomy
President (2020–2023)
Murilo Zerbini
Vice-President (2020–2023)
Stuart Siddell
Parent organization
International Union of Microbiological Societies, Virology Division
Affiliations Microbiology Society
Website OOjs UI icon edit-ltr-progressive.svg

The International Committee on Taxonomy of Viruses (ICTV) authorizes and organizes the taxonomic classification of and the nomenclatures for viruses. [1] [2] [3] The ICTV has developed a universal taxonomic scheme for viruses, and thus has the means to appropriately describe, name, and classify every virus that affects living organisms. The members of the International Committee on Taxonomy of Viruses are considered expert virologists. [4] The ICTV was formed from and is governed by the Virology Division of the International Union of Microbiological Societies. [5] Detailed work, such as delimiting the boundaries of species within a family, typically is performed by study groups of experts in the families. [2]



The International Committee on Nomenclature of Viruses (ICNV) was established in 1966, at the International Congress for Microbiology in Moscow, to standardize the naming of viruses. [6] The ICVN published its first report in 1971. [6] For viruses infecting vertebrates, the first report included 19 genera, 2 families, and a further 24 unclassified groups.[ citation needed ]

The ICNV was renamed the International Committee on Taxonomy of Viruses in 1974. [6]

Organisational structure

The organisation is divided into an executive committee, which includes fixed-term elected roles, and six subcommittees, each of which is further divided into numerous 'study groups', which each consist of one chair and a variable number of members dedicated to the taxonomy of a specific taxon, such as an order or family. This structure may be visualised as follows: [7]

Executive committee
  • Business Secretary
  • Proposals Secretary
  • Data Secretary


The objectives of the International Committee on Taxonomy of Viruses are:[ citation needed ]

  1. To develop an internationally agreed taxonomy for viruses.
  2. To establish internationally agreed names for virus taxa.
  3. To communicate the decisions reached concerning the classification and nomenclature of viruses to virologists by holding meetings and publishing reports.
  4. To maintain an official index of agreed names of virus taxa.
  5. To study the virus effects in modern society and their behaviour.

Principles of nomenclature

The ICTV's essential principles of virus nomenclature are:[ citation needed ]

The ICTV's universal virus classification system uses a slightly modified version of the standard biological classification system. It only recognises the taxa order, family, subfamily, genus, and species. When it is uncertain how to classify a species into a genus but its classification in a family is clear, it will be classified as an unassigned species of that family. Many taxa remain unranked. There are also, as of 2005, GenBank sequences assigned to 3,142 "species" which are not accounted for in the ICTV report (due to the way GenBank works, however, the actual number of proper species is probably significantly smaller). [2] The number of unidentified virus sequences is only expected to increase as the rate of virus sequencing increases dramatically. [2]

The ICTV has been strikingly successful in achieving stability, since their inception in 1962. Every genus and family recognized in the 1980s continued to be in use as of 2005, for example. [2]

Naming and changing taxa

Proposals for new names, name changes, and the establishment and taxonomic placement of taxa are handled by the executive committee of the ICTV in the form of proposals. All relevant ICTV subcommittees and study groups are consulted prior to a decision being taken.[ citation needed ]

The name of a taxon has no official status until it has been approved by ICTV, and names will only be accepted if they are linked to approved hierarchical taxa. If no suitable name is proposed for a taxon, the taxon may be approved and the name be left undecided until the adoption of an acceptable international name, when one is proposed to and accepted by ICTV. Names must not convey a meaning for the taxon which would seem to either exclude viruses which are rightfully members of that taxon, exclude members which might one day belong to that taxon, or include viruses which are members of different taxa.[ citation needed ]

Rules for taxa


A species name shall consist of as few words as practicable but must not consist only of a host name and the word virus. A species name must provide an appropriately unambiguous identification of the species. Numbers, letters, or combinations thereof may be used as species epithets where such numbers and letters are already widely used. However, newly designated serial numbers, letters or combinations thereof are not acceptable alone as species epithets. If a number or letter series is in existence it may be continued.[ citation needed ]


A virus genus is a group of related species that share some significant properties and often only differ in host range and virulence. A genus name must be a single word ending in the suffix -virus. Approval of a new genus must be accompanied by the approval of a type species.[ citation needed ]


A subfamily is a group of genera sharing certain common characters. The taxon shall be used only when it is needed to solve a complex hierarchical problem. A subfamily name must be a single word ending in the suffix -virinae.[ citation needed ]


A family is a group of genera, whether or not these are organized into subfamilies, sharing certain common characters with each other. A family name must be a single word ending in the suffix -viridae.[ citation needed ]


An order is a group of families sharing certain common characters. An order name must be a single word ending in the suffix -virales.

Rules for sub-viral agents

Rules concerned with the classification of viruses shall also apply to the classification of viroids. The formal endings for taxa of viroids are the word viroid for species, the suffix -viroid for genera, the suffix -viroinae for sub-families, should this taxon be needed, and -viroidae for families.[ citation needed ]

Retrotransposons are considered to be viruses in classification and nomenclature. Satellites and prions are not classified as viruses but are assigned an arbitrary classification as seems useful to workers in the particular fields.[ citation needed ]

Rules for orthography

  1. In formal taxonomic usage the accepted names of virus orders, families, subfamilies, and genera are printed in italics and the first letters of the names are capitalized. [8]
  2. Species names are printed in italics and have the first letter of the first word capitalized. Other words are not capitalized unless they are proper nouns, or parts of proper nouns.
  3. In formal usage, the name of the taxon shall precede the term for the taxonomic unit.

Classification of viruses discovered by metagenomics

Acknowledging the importance of viral metagenomics, the ICTV recognizes that genomes assembled from metagenomic data represent actual viruses and encourages their official classification following the same procedures as those used for viruses isolated and characterized using classical virology approaches. [9] [10]

ICTV reports

The ICTV has published reports of virus taxonomy about twice a decade since 1971 (listed below - "Reports"). The ninth ICTV report was published in December 2011; [11] the content is now freely available through the ICTV website. [12] Beginning in 2017 the tenth ICTV report will be published online on the ICTV website [13] and will be free to access with individual chapters updated on a rolling basis. The 2018 taxonomy is available online., [14] including a downloadable Excel spreadsheet of all recognized species.

ICTVdb database

ICTVdb is a species and isolate database that has been intended to serve as a companion to the ICTV taxonomy database. The development of ICTVdB has been supported by the ICTV since 1991 and was initially intended to aid taxonomic research. The database classifies viruses based primarily on their chemical characteristics, genomic type, nucleic acid replication, diseases, vectors, and geographical distribution, among other characteristics.[ citation needed ]

The database was developed at the Australian National University with support of the US National Science Foundation, and sponsored by the American Type Culture Collection. It uses the Description Language for Taxonomy (DELTA) system, a world standard for taxonomic data exchange, developed at Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO). DELTA is able to store a wide diversity of data and translate it into a language suitable for traditional reports and web publication. For example, ICTVdB does not itself contain genomic sequence information but can convert DELTA data into NEXUS format. [15] It can also handle large data inputs and is suited to compiling long lists of virus properties, text comments, and images.

ICTVdB has grown in concept and capability to become a major reference resource and research tool; in 1999 it was receiving over 30,000 combined online hits per day from its main site at the Australian National University, and two mirror sites based in the UK and United States. [16]

In 2011, the ICTV decided to suspend the ICTVdb project and web site. This decision was made after it became apparent that the taxonomy provided on the site was many years out of date, and that some of the information on the site was inaccurate due to problems with how the database was being queried and processed to support the natural language output of the ICTVdb web site. The ICTV has begun discussions on how best to fix these problems, but decided that the time frame for updates and error correction were sufficiently long that it was best to take the site down rather than perpetuate the release of inaccurate information.[ citation needed ] As of August 2013, the database remains on hold. [3] According to some views, "ICTV should also promote the use of a public database to replace the ICTV database as a store of the primary metadata of individual viruses, and should publish abstracts of the ICTV Reports in that database, so that they are 'Open Access'." [3]


See also

Related Research Articles

Order is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized by the nomenclature codes. An immediately higher rank, superorder, is sometimes added directly above order, with suborder directly beneath order. An order can also be defined as a group of related families.

Virus classification is the process of naming viruses and placing them into a taxonomic system similar to the classification systems used for cellular organisms.

<i>Mononegavirales</i> Order of viruses

Mononegavirales is an order of negative-strand RNA viruses which have nonsegmented genomes. Some common members of the order are Ebola virus, human respiratory syncytial virus, measles virus, mumps virus, Nipah virus, and rabies virus. All of these viruses cause significant disease in humans. Many other important pathogens of nonhuman animals and plants are also in the group. The order includes eleven virus families: Artoviridae, Bornaviridae, Filoviridae, Lispiviridae, Mymonaviridae, Nyamiviridae, Paramyxoviridae, Pneumoviridae, Rhabdoviridae, Sunviridae, and Xinmoviridae.

<i>Marburgvirus</i> Genus of virus

The genus Marburgvirus is the taxonomic home of Marburg marburgvirus, whose members are the two known marburgviruses, Marburg virus (MARV) and Ravn virus (RAVV). Both viruses cause Marburg virus disease in humans and nonhuman primates, a form of viral hemorrhagic fever. Both are Select agents, World Health Organization Risk Group 4 Pathogens, National Institutes of Health/National Institute of Allergy and Infectious Diseases Category A Priority Pathogens, Centers for Disease Control and Prevention Category A Bioterrorism Agents, and are listed as Biological Agents for Export Control by the Australia Group.

<i>Ebolavirus</i> Genus of viruses

The genus Ebolavirus is a virological taxon included in the family Filoviridae, order Mononegavirales. The members of this genus are called ebolaviruses, and encode their genome in the form of single-stranded negative-sense RNA. The six known virus species are named for the region where each was originally identified: Bundibugyo ebolavirus, Reston ebolavirus, Sudan ebolavirus, Taï Forest ebolavirus, Zaire ebolavirus, and Bombali ebolavirus. The last is the most recent species to be named and was isolated from Angolan free-tailed bats in Sierra Leone.

<i>Influenza B virus</i> Species of virus

Influenza B virus is the only species in the genus Betainfluenzavirus in the virus family Orthomyxoviridae.

Bovine alphaherpesvirus 2 (BoHV2) is a virus of the family Herpesviridae that causes two diseases in cattle, bovine mammillitis and pseudo-lumpy skin disease. BoHV2 is similar in structure to human herpes simplex virus.

Pepper mild tigré virus (PepMTV) is a plant pathogenic virus of the family Geminiviridae. It was demoted from species status in 2002.

Pepper golden mosaic virus is a plant pathogenic virus of the family Geminiviridae. It affects Capsicum annuum and all tomatoes. It was first discovered in Texas in 1987, and was called Texas Pepper Virus, and a two years later in Mexico after it destroyed up to 100% of plants in afflicted fields in the autumn of 1989, mainly in north-west Mexico.

Anelloviridae is a family of viruses. They are classified as vertebrate viruses and have a non-enveloped capsid, which is round with isometric, icosahedral symmetry and has a triangulation number of 3.

<i>Benyvirus</i> Genus of viruses

Benyvirus is a genus of viruses, in the family Benyviridae. Plant serve as natural hosts. There are four species in this genus. Diseases associated with this genus include: BNYVV: rhizomania.

<span class="mw-page-title-main">Taxonomic rank</span> Level in a taxonomic hierarchy

In biological classification, taxonomic rank is the relative level of a group of organisms in an ancestral or hereditary hierarchy. A common system consists of species, genus, family, order, class (clade), phylum, kingdom, domain. The study of taxonomy is also called cladistics.

<i>Carlavirus</i> Genus of viruses

Carlavirus, formerly known as the "Carnation latent virus group", is a genus of viruses in the order Tymovirales, in the family Betaflexiviridae. Plants serve as natural hosts. There are 53 species in this genus. Diseases associated with this genus include: mosaic and ringspot symptoms.

Aspiviridae Family of viruses

Aspiviridae, formerly Ophioviridae, is a family of segmented negative-strand RNA viruses which infect plants. Member viruses are characterized by an elongated and highly filamentous and flexible nucleocapsid with helical symmetry. It is a monotypic taxon containing only one genus, Ophiovirus. Aspiviridae is also the only family in the order Serpentovirales, which in turn is the only order in the class Milneviricetes.

The species Taï Forest ebolavirus is a virological taxon included in the genus Ebolavirus, family Filoviridae, order Mononegavirales. The species has a single virus member, Taï Forest virus (TAFV). The members of the species are called Taï Forest ebolaviruses.

<i>Betacoronavirus 1</i> Species of virus

Betacoronavirus 1 is a species of coronavirus which infects humans and cattle. The infecting virus is an enveloped, positive-sense, single-stranded RNA virus and is a member of the genus Betacoronavirus and subgenus Embecovirus. Like other embecoviruses, it has an additional shorter spike-like surface protein called hemagglutinin esterase (HE) as well as the larger coronavirus spike protein.

Acara orthobunyavirus (ACAV) is a species in the genus Orthobunyavirus, belonging to the Capim serogroup. It is isolated from sentinel mice, Culex species, and the rodent Nectomys squamipes in Pará, Brazil and in Panama. The symptoms of the Acará virus is death. Sometimes reported to cause disease in humans.

<i>Avian metaavulavirus 2</i> Species of virus

Avian metaavulavirus 2, formerly Avian paramyxovirus 2, is a species of virus belonging to the family Paramyxoviridae and genus Metaavulavirus. The virus is a negative strand RNA virus containing a monopartite genome. Avian metaavulavirus 2 is one of nine species belonging to the genus Metaavulavirus. The most common serotype of Avulavirinae is serotype 1, the cause of Newcastle disease (ND). Avian metaavulavirus 2 has been known to cause disease, specifically mild respiratory infections in domestic poultry, including turkeys and chickens, and has many economic effects on egg production and poultry industries. The virus was first isolated from a strain in Yucaipa, California in 1956. Since then, other isolates of the virus have been isolated worldwide.

In virology, realm is the highest taxonomic rank established for viruses by the International Committee on Taxonomy of Viruses (ICTV), which oversees virus taxonomy. Six virus realms are recognized and united by specific highly conserved traits:


Ribozyviria is a realm of satellite nucleic acids. Established in ICTV TaxoProp 2020.012D, the realm is named after the presence of genomic and antigenomic ribozymes of the Deltavirus type. Additional common features include a rod-like structure, a RNA-binding "delta antigen" encoded in the genome, and animal hosts. Furthermore, the size range of the genomes of these viruses is between around 1547-1735nt, they encode a hammerhead ribozyme or a hepatitis delta virus ribozyme, and their coding capacity only involves one conserved protein. Most lineages of this realm are poorly understood, the notable exception being members of the genus Deltavirus, the causal agents of Hepatitis D in humans.


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