ICTV Virus Taxonomy Profiles

The family Globuloviridae comprises enveloped viruses with linear, double-stranded DNA genomes of about 21–28 kbp. The virions are spherical with a diameter of 70–100 nm. No information is available about genome replication. Globuloviruses infect hyperthermophilic archaea belonging to the genera Pyrobaculum and Thermoproteus, which thrive in extreme geothermal environments. Infection does not cause lysis of host cells and is noncytocidal. The viral genome does not integrate into the host chromosome. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Globuloviridae, which is available at www.ictv.global/report/globuloviridae.

The Papillomaviridae is a family of small, non-enveloped viruses with double-stranded DNA genomes of 5 748 to 8 607 bp. Their classification is based on pairwise nucleotide sequence identity across the L1 open reading frame. Members of the Papillomaviridae primarily infect mucosal and keratinised epithelia, and have been isolated from fish, reptiles, birds and mammals. Despite a long co-evolutionary history with their hosts, some papillomaviruses are pathogens of their natural host species. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Papillomaviridae, which is available at http://www.ictv.global/report/papillomaviridae.

The Togaviridae is a family of small, enveloped viruses with single-stranded, positive-sense RNA genomes of 10–12 kb. Within the family, the genus Alphavirus includes a large number of diverse species, while the genus Rubivirus includes the single species Rubella virus. Most alphaviruses are mosquito-borne and are pathogenic in their vertebrate hosts. Many are important human and veterinary pathogens (e.g. chikungunya virus and eastern equine encephalitis virus). Rubella virus is transmitted by respiratory routes among humans. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Togaviridae, which is available at www.ictv.global/report/togaviridae.

Members of the family Avsunviroidae have a single-stranded circular RNA genome that adopts a rod-like or branched conformation and can form, in the strands of either polarity, hammerhead ribozymes involved in their replication in plastids through a symmetrical RNA–RNA rolling-circle mechanism. These viroids lack the central conserved region typical of members of the family Pospiviroidae. The family Avsunviroidae includes three genera, Avsunviroid, Pelamoviroid and Elaviroid, with a total of four species. This is a summary of the ICTV Report on the taxonomy of the family Avsunviroidae, which is available at http://www.ictv.global/report/avsunviroidae.

The family Plasmaviridae includes bacterial viruses with slightly pleomorphic, enveloped virions with a diameter of 50–125 nm. Virions contain infectious, circular, supercoiled dsDNA molecule(s) of approximately 12 kbp. Plasmaviruses infect Acholeplasma species, wall-less bacteria of the class Mollicutes, and are released by budding through the cell membrane without causing host cell lysis. Although the temperate bacteriophage Acholeplasma virus L2 of Acholeplasma laidlawii is currently the only classified plasmavirus, related prophages reside in the genomes of different Acholeplasma species, where they are integrated into tRNA genes. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Plasmaviridae, which is available at www.ictv.global/report/plasmaviridae.

Guttaviridae is a family of enveloped viruses infecting hyperthermophilic archaea. The virions are ovoid or droplet-shaped, with a diameter of 55–80 nm and a length of 75–130 nm. The genome is a circular dsDNA molecule of around 14–20 kbp. The droplet-shaped morphology is unprecedented among viruses of bacteria and eukaryotes and represents a group of archaea-specific virion morphotypes. The family includes two genera, Alphaguttavirus and Betaguttavirus, each with a single species. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of Guttaviridae, which is available at www.ictv.global/report/guttaviridae.

The Partitiviridae is a family of small, isometric, non-enveloped viruses with bisegmented double-stranded (ds) RNA genomes of 3–4.8 kbp. The two genome segments are individually encapsidated. The family has five genera, with characteristic hosts for members of each genus: either plants or fungi for genera Alphapartitivirus and Betapartitivirus, fungi for genus Gammapartitivirus, plants for genus Deltapartitivirus and protozoa for genus Cryspovirus. Partitiviruses are transmitted intracellularly via seeds (plants), oocysts (protozoa) or hyphal anastomosis, cell division and sporogenesis (fungi); there are no known natural vectors. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Partitiviridae, which is available at www.ictv.global/report/partitiviridae.

Members of the family Pleolipoviridae (termed pleolipoviruses) are pseudo-spherical and pleomorphic archaeal viruses. The enveloped virion is a simple membrane vesicle, which encloses different types of DNA genomes of approximately 7–16 kbp (or kilonucleotides). Typically, virions contain a single type of transmembrane (spike) protein at the envelope and a single type of membrane protein, which is embedded in the envelope and located in the internal side of the membrane. All viruses infect extremely halophilic archaea in the class Halobacteria (phylum Euryarchaeota). Pleolipoviruses have a narrow host range and a persistent, non-lytic life cycle. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Pleolipoviridae which is available at www.ictv.global/report/pleolipoviridae.

The family Hepeviridae includes enterically transmitted small non-enveloped positive-sense RNA viruses. It includes the genera Piscihepevirus, whose members infect fish, and Orthohepevirus, whose members infect mammals and birds. Members of the genus Orthohepevirus include hepatitis E virus, which is responsible for self-limiting acute hepatitis in humans and several mammalian species; the infection may become chronic in immunocompromised individuals. Extrahepatic manifestations of Guillain–Barré syndrome, neuralgic amyotrophy, glomerulonephritis and pancreatitis have been described in humans. Avian hepatitis E virus causes hepatitis–splenomegaly syndrome in chickens. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Hepeviridae, which is available at www.ictv.global/report/hepeviridae.

The family Picornaviridae comprises small non-enveloped viruses with RNA genomes of 6.7 to 10.1 kb, and contains >30 genera and >75 species. Most of the known picornaviruses infect mammals and birds, but some have also been detected in reptiles, amphibians and fish. Many picornaviruses are important human and veterinary pathogens and may cause diseases of the central nervous system, heart, liver, skin, gastrointestinal tract or upper respiratory tract. Most picornaviruses are transmitted by the faecal–oral or respiratory routes. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Picornaviridae, which is available at www.ictv.global/report/picornaviridae.

The family Virgaviridae is a family of plant viruses with rod-shaped virions, a ssRNA genome with a 3′-terminal tRNA-like structure and a replication protein typical of alpha-like viruses. Differences in the number of genome components, genome organization and the mode of transmission provide the basis for genus demarcation. Tobacco mosaic virus (genus Tobamovirus) was the first virus to be discovered (in 1886); it is present in high concentrations in infected plants, is extremely stable and has been extensively studied. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Virgaviridae, which is available at www.ictv.global/report/virgaviridae.

The Ophioviridae is a family of filamentous plant viruses, with single-stranded negative, and possibly ambisense, RNA genomes of 11.3–12.5 kb divided into 3–4 segments, each encapsidated separately. Virions are naked filamentous nucleocapsids, forming kinked circles of at least two different contour lengths. The sole genus, Ophiovirus, includes seven species. Four ophioviruses are soil-transmitted and their natural hosts include trees, shrubs, vegetables and bulbous or corm-forming ornamentals, both monocots and dicots. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Ophioviridae, which is available at http://www.ictv.global/report/ophioviridae.

The Corticoviridae is a family of icosahedral, internal-membrane-containing viruses with double-stranded circular DNA genomes of approximately 10 kb. Only one species, Pseudoalteromonas virus PM2, has been recognized. Pseudoalteromonas virus PM2 infects Gram-negative bacteria and was isolated from seawater in 1968. Pseudoalteromonas virus PM2 is the first bacterial virus in which the presence of lipids in the virion has been demonstrated. Viral lipids are acquired selectively during virion assembly from the host cytoplasmic membrane. The outer protein capsid is an icosahedron with a pseudo T=21 symmetry. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Corticoviridae, which is available at www.ictv.global/report/corticoviridae.

Iflaviridae is a family of small non-enveloped viruses with monopartite, positive-stranded RNA genomes of approximately 9–11 kilobases. Viruses of all classified species infect arthropod hosts, with the majority infecting insects. Both beneficial and pest insects serve as hosts, and infections can be symptomless (Nilaparvatalugens honeydew virus 1) or cause developmental abnormalities (deformed wing virus), behavioural changes (sacbrood virus) and premature mortality (infectious flacherie virus). The host range has not been examined for most members. The most common route of infection for iflaviruses is the ingestion of virus-contaminated food sources. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Iflaviridae, which is available at www.ictv.global/report/iflaviridae.

Dicistroviridae is a family of small non-enveloped viruses with monopartite, linear, positive-sense RNA genomes of approximately 8–10 kb. Viruses of all classified species infect arthropod hosts, with some having devastating economic consequences, such as acute bee paralysis virus in domesticated honeybees and taura syndrome virus in shrimp farming. Conversely, the host specificity and other desirable traits exhibited by several members of this group make them potential natural enemies for intentional use against arthropod pests, such as triatoma virus against triatomine bugs that vector Chagas disease. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Dicistroviridae which is available at www.ictv.global/report/dicistroviridae.

The geminiviruses are a family of small, non-enveloped viruses with single-stranded, circular DNA genomes of 2500–5200 bases. Geminiviruses are transmitted by various types of insect (whiteflies, leafhoppers, treehoppers and aphids). Members of the genus Begomovirus are transmitted by whiteflies, those in the genera Becurtovirus, Curtovirus, Grablovirus, Mastrevirus and Turncurtovirus are transmitted by specific leafhoppers, the single member of the genus Topocuvirus is transmitted by a treehopper and one member of the genus Capulavirus is transmitted by an aphid. Geminiviruses are plant pathogens causing economically important diseases in most tropical and subtropical regions of the world. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Geminiviridae which is available at www.ictv.global/report/geminiviridae.

The family Ascoviridae includes viruses with circular dsDNA genomes of 100–200 kbp characterized by oblong enveloped virions of 200–400 nm in length. Ascoviruses mainly infect lepidopteran larvae and are mechanically transmitted by parasitoid wasps in which they may also replicate. Most known members belong to the genus Ascovirus, except one virus, that of the genus Toursvirus, which replicates in both its lepidopteran and parasitoid vector hosts. Ascoviruses cause high mortality among economically important insect pests, thereby controlling insect populations. This is a summary of the current International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Ascoviridae, which is available at www.ictv.global/report/ascoviridae.