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Pseudoviridae is a family of reverse-transcribing viruses with long terminal repeats (LTRs) belonging to the order Ortervirales. Pseudoviruses are commonly found integrated in the genomes of diverse plants, fungi and animals and are broadly known as Ty1/Copia LTR retrotransposons. Inside the cell, they form icosahedral virus particles, but unlike most other viruses, do not have an extracellular phase. This is a summary of the ICTV Report on the family Pseudoviridae, which is available at ictv.global/report/pseudoviridae.

Nanoviridae is a family of plant viruses (nanovirids) whose members have small isometric virions and multipartite, circular, single-stranded (css) DNA genomes. Each of the six (genus Babuvirus) or eight (genus Nanovirus) genomic DNAs is 0.9–1.1 kb and is separately encapsidated. Many isolates are associated with satellite-like cssDNAs (alphasatellites) of 1.0–1.1 kb. Hosts are eudicots, predominantly legumes (genus Nanovirus), and monocotyledons, predominantly in the order Zingiberales (genus Babuvirus). Nanovirids require a virus-encoded helper factor for transmission by aphids in a circulative, non-propagative manner. This is a summary of the ICTV Report on the family Nanoviridae, which is available at ictv.global/report/nanoviridae.

Ovaliviridae is a family of enveloped viruses with a linear dsDNA genome. The virions are ellipsoidal, and contain a multi-layered spool-like capsid. The viral genome is presumably replicated through protein priming by a putative DNA polymerase encoded by the virus. Progeny virions are released through hexagonal openings resulting from the rupture of virus-associated pyramids formed on the surface of infected cells. The only known host is a hyperthermophilic archaeon of the genus Sulfolobus . This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Ovaliviridae, which is available at ictv.global/report/ovaliviridae.

Viruses in the family Redondoviridae have a circular genome of 3.0 kb with three open reading frames. The packaged genome is inferred to be single-stranded DNA by analogy to related viruses. Redondoviruses were discovered through metagenomic sequencing methods in samples from human subjects and are inferred to replicate in humans. Evidence of redondovirus infection is associated with periodontitis and critical illness, but redondoviruses have not been shown to be the causative agent of any diseases. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Redondoviridae, which is available at ictv.global/report/redondoviridae.

[EN] Members of the family Pospiviroidae have single-stranded circular RNA genomes that adopt a rod-like or a quasi-rod-like conformation. These genomes contain a central conserved region that is involved in replication in the nucleus through an asymmetric RNA-RNA rolling-circle mechanism. Members of the family Pospiviroidae lack the hammerhead ribozymes that are typical of viroids classified in the family Avsunviroidae. The family Pospiviroidae includes the genera Apscaviroid, Cocadviroid, Coleviroid, Hostuviroid and Pospiviroid, with >25 species. This is a summary of the ICTV Report on the family Pospiviroidae, which is available at ictv.global/report/pospiviroidae., Production of this summary, the online chapter, and associated resources was funded by a grant from the Wellcome Trust (WT108418AIA).

The family Roniviridae includes the genus Okavirus for three species of viruses with enveloped, rod-shaped virions. The monopartite, positive-sense ssRNA genome (26–27 kb) contains five canonical long open reading frames (ORFs). ORF1a encodes polyprotein pp1a containing proteinase domains. ORF1b is expressed as a large polyprotein pp1ab by ribosomal frameshifting from ORF1a and encodes replication enzymes. ORF2 encodes the nucleoprotein. ORF3 encodes two envelope glycoproteins. ORFX encodes a putative double membrane-spanning protein. Roniviruses infect shrimp but only yellow head virus is highly pathogenic. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Roniviridae, which is available at ictv.global/report/roniviridae.

The family Botourmiaviridae includes viruses infecting plants and filamentous fungi containing a positive-sense, ssRNA genome that can be mono- or multi-segmented. Genera in the family include: Ourmiavirus (plant viruses), and Botoulivirus, Magoulivirus and Scleroulivirus (fungal viruses). This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the family Botourmiaviridae, which is available at ictv.global/report/botourmiaviridae.

Viruses in the family Closteroviridae have a mono-, bi- or tripartite positive-sense RNA genome of 13–19 kb, and non-enveloped, filamentous particles 650–2200 nm long and 12 nm in diameter. They infect plants, mainly dicots, many of which are fruit crops. This is a summary of the ICTV Report on the family Closteroviridae, which is available at ictv.global/report/closteroviridae.

International audience; The family Spiraviridae includes viruses that replicate in hyperthermophilic archaea from the genus Aeropyrum. The non-enveloped, hollow, cylindrical virions are formed from a coiling fibre that consists of two intertwining halves of a single circular nucleoprotein filament. A short appendage protrudes from each end of the cylindrical virion. The genome is circular, positive-sense, single-stranded DNA of 24 893 nucleotides. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) report on the family Spiraviridae, which is available at ictv.global/report/spiraviridae.

Members of the family Herelleviridae are bacterial viruses infecting members of the phylum Firmicutes. The virions have myovirus morphology and virus genomes comprise a linear dsDNA of 125–170 kb. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Herelleviridae, which is available at ictv.global/report/herelleviridae.

Caulimoviridae is a family of non-enveloped reverse-transcribing plant viruses with non-covalently closed circular dsDNA genomes of 7.1–9.8 kbp in the order Ortervirales. They infect a wide range of monocots and dicots. Some viruses cause economically important diseases of tropical and subtropical crops. Transmission occurs through insect vectors (aphids, mealybugs, leafhoppers, lace bugs) and grafting. Activation of infectious endogenous viral elements occurs in Musa balbisiana, Petunia hybrida and Nicotiana edwardsonii. However, most endogenous caulimovirids are not infectious. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Caulimoviridae, which is available at ictv.global/report/caulimoviridae.

Members of the family Nudiviridae are large dsDNA viruses with distinctive rod-shaped nucleocapsids and circular genomes of 96-232 kbp. Nudiviruses have been identified from a diverse range of insects and crustaceans and are closely related to baculoviruses. This is a summary of the International Committee on Taxonomy of Viruses Report on the taxonomy of the family Nudiviridae, which is available at ictv.global/report/nudiviridae.

Metaviridae is a family of retrotransposons and reverse-transcribing viruses with long terminal repeats belonging to the order Ortervirales. Members of the genera Errantivirus and Metavirus include, respectively, Saccharomyces cerevisiae Ty3 virus and its Gypsy-like relatives in drosophilids. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Metaviridae, which is available at ictv.global/report/metaviridae.

Members of the family Nairoviridae produce enveloped virions with three single-stranded RNA segments comprising 17.1 to 22.8 kb in total. These viruses are maintained in arthropods and transmitted by ticks to mammals or birds. Crimean-Congo hemorrhagic fever virus is tick-borne and is endemic in most of Asia, Africa, Southern and Eastern Europe whereas Nairobi sheep disease virus, which is also tick-borne, causes lethal haemorrhagic gastroenteritis in small ruminants in Africa and India. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Nairoviridae, which is available at ictv.global/report/nairoviridae.

The family Hepadnaviridae comprises small enveloped viruses with a partially double-stranded DNA genome of 3.0–3.4 kb. All family members express three sets of proteins (preC/C, polymerase and preS/S) and replication involves reverse transcription within nucleocapsids in the cytoplasm of hepatocytes. Hepadnaviruses are hepatotropic and infections may be transient or persistent. There are five genera: Parahepadnavirus, Metahepadnavirus, Herpetohepadnavirus, Avihepadnavirus and Orthohepadnavirus. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Hepadnaviridae, which is available at ictv.global/report/hepadnaviridae.

Wellcome Trust (WT108418AIA); Fundac?a?o de Amparo a? Pesquisa do Estado de Sa?o Paulo, Brazil (17/13981?0) Centers for Disease Control and Prevention. Fort Collins, CO, USA. United States Department of Agriculture. Agricultural Research Service. Fort Pierce, FL, USA. D. I. Ivanovsky Institute of Virology. Moscow, Russia. Friedrich-Loeffler-Institut. Greifswald-Insel Riems. Germany. Colorado State University. Fort Collins, CO, USA. Public Health Agency of Canada. Winnipeg, MB, Canada. University of Campinas. Campinas, SP, Brazil. Charit?-Universit?tsmedizin Berlin. Berlin, Germany / Humboldt-University Berlin. Berlin, Germany / Berlin Institute of Health. Berlin, Germany. Minist?rio da Sa?de. Secretaria de Vigil?ncia em Sa?de. Instituto Evandro Chagas. Ananindeua, PA, Brasil. MRC-University of Glasgow Centre for Virus Research. Glasgow, UK. Peribunyaviruses are enveloped and possess three distinct, single-stranded, negative-sense RNA segments comprising 11.2?12.5kb in total. The family includes globally distributed viruses in the genera Orthobunyavirus, Herbevirus, Pacuvirus and Shangavirus. Most viruses are maintained in geographically-restricted vertebrate?arthropod transmission cycles that can include transovarial transmission from arthropod dam to offspring. Others are arthropod-specific. Arthropods can be persistently infected. Human infection occurs through blood feeding by an infected vector arthropod. Infections can result in a diversity of human and veterinary clinical outcomes in a strain-specific manner. Segment reassortment is evident between some peribunyaviruses

The family Caliciviridae includes viruses with single-stranded, positive-sense RNA genomes of 7.4–8.3 kb. The most clinically important representatives are human noroviruses, which are a leading cause of acute gastroenteritis in humans. Virions are non-enveloped with icosahedral symmetry. Members of seven genera infect mammals (Lagovirus, Norovirus, Nebovirus, Recovirus, Sapovirus, Valovirus and Vesivirus), members of two genera infect birds (Bavovirus and Nacovirus), and members of two genera infect fish (Minovirus and Salovirus). This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Caliciviridae, which is available at ictv.global/report/caliciviridae.

The family Paramyxoviridae consists of large enveloped RNA viruses infecting mammals, birds, reptiles and fish. Many paramyxoviruses are host-specific and several, such as measles virus, mumps virus, Nipah virus, Hendra virus and several parainfluenza viruses, are pathogenic for humans. The transmission of paramyxoviruses is horizontal, mainly through airborne routes; no vectors are known. This is a summary of the current International Committee on Taxonomy of Viruses (ICTV) Report on the family Paramyxoviridae. which is available at ictv.global/report/paramyxoviridae.

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.

Members of the family Chrysoviridae are isometric, non-enveloped viruses with segmented, linear, dsRNA genomes. There are 3–7 genomic segments, each of which is individually encapsidated. Chrysoviruses infect fungi, plants and possibly insects, and may cause hypovirulence in their fungal hosts. Chrysoviruses have no known vectors and lack an extracellular phase to their replication cycle; they are transmitted via intracellular routes within an individual during hyphal growth, in asexual or sexual spores, or between individuals via hyphal anastomosis, Production of this summary, the online chapter and associated resources was funded by a grant from the Wellcome Trust (WT108418AIA).

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.