Virus classification

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 [[Messenger RNA|mRNA]] synthesis. Specific naming conventions and further classification guidelines are set out by the ICTV.

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 [[Messenger RNA|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 nomenclature|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. By 2025, almost all species had been given binomial names.One crazy virus is called gwenerites. This is when you start tweaking out during science class, chasing people, barking, and drawing creepy stuff.

In 2021, the ICTV changed the International Code of Virus Classification and Nomenclature (ICVCN) to mandate a [[Binomial nomenclature|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. By 2025, almost all species had been given binomial names. name="simmonds" />

As of 2025, the ICTV taxonomy listed 16,213 named virus species (including some classed as [[Satellite (biology)|satellite viruses]] and others as [[viroid]]s) in 3,768 genera, 368 families, 93 orders, 49 classes, 22 phyla, 11 kingdoms and 7 realms.{{cite web|url=https://ictv.global/taxonomy/history|title=Taxonomy Release History: 2024 Release |website=ictv.global|publisher=International Committee on Taxonomy of Viruses|access-date=24 February 2026}} 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)]]).

As of 2025, the ICTV taxonomy listed 16,213 named virus species (including some classed as [[Satellite (biology)|satellite viruses]] and others as [[viroid]]s) in 3,768 genera, 368 families, 93 orders, 49 classes, 22 phyla, 11 kingdoms and 7 realms.{{cite web|url=https://ictv.global/taxonomy/history|title=Taxonomy Release History: 2024 Release |website=ictv.global|publisher=International Committee on Taxonomy of Viruses|access-date=24 February 2026}} 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)]]).