Editing Virus classification (section)

{{short description|Organisation of viruses into a taxonomic system}}
[[File:Virus classification L Pengo vflip.svg|thumb|Virus classification]]
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'''Virus classification''' is the process of naming [[virus]]es and placing them into a [[taxonomy (biology)|taxonomic]] system similar to the classification systems used for [[cell (biology)|cellular organisms]].

Viruses are classified by [[phenotypic]] characteristics, such as [[Virus#Structure|morphology]], [[nucleic acid]] type, mode of replication, [[Host (biology)|host organism]]s, and the type of [[disease]] they cause. The formal taxonomic classification of viruses is the responsibility of the [[International Committee on Taxonomy of Viruses]] (ICTV) system, although the [[Baltimore classification]] system can be used to place viruses into one of seven groups based on their manner of mRNA synthesis. Specific naming conventions and further classification guidelines are set out by the ICTV.

In 2021, the ICTV changed the International Code of Virus Classification and Nomenclature (ICVCN) to mandate a binomial format (genus|| ||species) for naming new viral species similar to that used for cellular organisms; the names of species coined prior to 2021 are gradually being converted to the new format, a process planned for completion by the end of 2023.{{Update needed|date=August 2024|reason=Was this completed by the end of 2023?}}

As of 2022, the ICTV taxonomy listed 11,273 named virus species (including some classed as satellite viruses and others as viroids) in 2,818 genera, 264 families, 72 orders, 40 classes, 17 phyla, 9 kingdoms and 6 realms.<ref name="Virus Taxonomy 2022">{{cite web|url=https://ictv.global/taxonomy|title=Virus Taxonomy: 2022 v3 Release|website=ictv.global|publisher=International Committee on Taxonomy of Viruses|access-date=5 January 2024}}</ref> However, the number of named ''viruses'' considerably exceeds the number of named virus ''species'' since, by contrast to the classification systems used elsewhere in biology, a virus "species" is a collective name for a group of (presumably related) viruses sharing certain common features (see below). Also, the use of the term "kingdom" in virology does not equate to its usage in other biological groups, where it reflects high level groupings that separate completely different kinds of organisms (see [[Kingdom (biology)]]).