An RNA virus is a

virus A virus is a submicroscopic infectious agent that replicates only inside the living Cell (biology), cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are ...

characterized by a ribonucleic acid (

RNA Ribonucleic acid (RNA) is a polymeric molecule that is essential for most biological functions, either by performing the function itself (non-coding RNA) or by forming a template for the production of proteins (messenger RNA). RNA and deoxyrib ...

) based

genome A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as ...

. The genome can be single-stranded RNA ( ssRNA) or double-stranded (

dsRNA Ribonucleic acid (RNA) is a polymeric molecule that is essential for most biological functions, either by performing the function itself ( non-coding RNA) or by forming a template for the production of proteins ( messenger RNA). RNA and deoxy ...

). Notable human diseases caused by RNA viruses include

influenza Influenza, commonly known as the flu, is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These sympto ...

SARS Severe acute respiratory syndrome (SARS) is a viral respiratory disease of zoonotic origin caused by the virus SARS-CoV-1, the first identified strain of the SARS-related coronavirus. The first known cases occurred in November 2002, and the ...

MERS Middle East respiratory syndrome (MERS) is a viral respiratory infection caused by '' Middle East respiratory syndrome–related coronavirus'' (MERS-CoV). Symptoms may range from none, to mild, to severe depending on age and risk level. Typi ...

COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by the coronavirus SARS-CoV-2. In January 2020, the disease spread worldwide, resulting in the COVID-19 pandemic. The symptoms of COVID‑19 can vary but often include fever ...

Dengue virus Dengue virus (DENV) is the cause of dengue fever. It is a mosquito-borne, single positive-stranded RNA virus of the family ''Flaviviridae''; genus '' Flavivirus''. Four serotypes of the virus have been found, and a reported fifth has yet to be ...

hepatitis C Hepatitis C is an infectious disease caused by the hepatitis C virus (HCV) that primarily affects the liver; it is a type of viral hepatitis. During the initial infection period, people often have mild or no symptoms. Early symptoms can include ...

hepatitis E Hepatitis E is inflammation of the liver caused by infection with the hepatitis E virus (HEV); it is a type of viral hepatitis. Hepatitis E has mainly a fecal-oral transmission route that is similar to hepatitis A, although the viruses are u ...

, West Nile fever,

Ebola virus disease Ebola, also known as Ebola virus disease (EVD) and Ebola hemorrhagic fever (EHF), is a viral hemorrhagic fever in humans and other primates, caused by ebolaviruses. Symptoms typically start anywhere between two days and three weeks after infe ...

rabies Rabies is a viral disease that causes encephalitis in humans and other mammals. It was historically referred to as hydrophobia ("fear of water") because its victims panic when offered liquids to drink. Early symptoms can include fever and abn ...

polio Poliomyelitis ( ), commonly shortened to polio, is an infectious disease caused by the poliovirus. Approximately 75% of cases are asymptomatic; mild symptoms which can occur include sore throat and fever; in a proportion of cases more severe ...

mumps MUMPS ("Massachusetts General Hospital Utility Multi-Programming System"), or M, is an imperative, high-level programming language with an integrated transaction processing key–value database. It was originally developed at Massachusetts Gen ...

, and

measles Measles (probably from Middle Dutch or Middle High German ''masel(e)'', meaning "blemish, blood blister") is a highly contagious, Vaccine-preventable diseases, vaccine-preventable infectious disease caused by Measles morbillivirus, measles v ...

. All known RNA viruses, that is viruses that use a homologous RNA-dependent polymerase for replication, are categorized by the

International Committee on Taxonomy of Viruses The International Committee on Taxonomy of Viruses (ICTV) authorizes and organizes the taxonomic classification of and the nomenclature for viruses. The ICTV develops a universal taxonomic scheme for viruses, and thus has the means to appropri ...

(ICTV) into the realm ''

Riboviria ''Riboviria'' is a Realm (virology), realm of viruses that includes all viruses that use a homologous RNA-dependent polymerase for replication. It includes RNA viruses that Genetic code, encode an RNA-dependent RNA polymerase, as well as Pararnavi ...

''. This includes RNA viruses belonging to ''Group III'', ''Group IV'' or ''Group V'' of the

Baltimore classification Baltimore classification is a system used to classify viruses based on their manner of messenger RNA (mRNA) synthesis. By organizing viruses based on their manner of mRNA production, it is possible to study viruses that behave similarly as a disti ...

system as well as ''Group VI. Group VI'' viruses are

retrovirus A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. After invading a host cell's cytoplasm, the virus uses its own reverse transcriptase e ...

es, viruses with RNA genetic material that use

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

intermediates in their life cycle including

HIV-1 The subtypes of HIV include two main subtypes, known as HIV type 1 (HIV-1) and HIV type 2 (HIV-2). These subtypes have distinct genetic differences and are associated with different epidemiological patterns and clinical characteristics. HIV-1 e ...

and

HIV-2 The subtypes of HIV include two main subtypes, known as HIV type 1 (HIV-1) and HIV type 2 (HIV-2). These subtypes have distinct genetic differences and are associated with different epidemiological patterns and clinical characteristics. HIV-1 ex ...

which cause

AIDS The HIV, human immunodeficiency virus (HIV) is a retrovirus that attacks the immune system. Without treatment, it can lead to a spectrum of conditions including acquired immunodeficiency syndrome (AIDS). It is a Preventive healthcare, pr ...

. The majority of such RNA viruses fall into the kingdom '' Orthornavirae'' and the rest have a positioning not yet defined.TaxoPro
2019.006G
/ref> The realm does not contain all RNA viruses: '' Deltavirus'', ''

Avsunviroidae The ''Avsunviroidae'' are a family of viroids. There are five species in three genera ('' Avsunviroid'', '' Elaviroid'' and '' Pelamoviroid''). They consist of RNA genomes between 246 and 375 nucleotides in length. They are single-stranded cov ...

'', and '' Pospiviroidae'' are taxa of RNA viruses that were mistakenly included in 2019, but corrected in 2020.

Characteristics

Single-stranded RNA viruses and RNA Sense

RNA viruses can be further classified according to the sense or polarity of their RNA into

negative-sense In molecular biology and genetics, the sense of a nucleic acid molecule, particularly of a strand of DNA or RNA, refers to the nature of the roles of the strand and its complement in specifying a sequence of amino acids. Depending on the context, ...

and positive-sense, or ambisense RNA viruses. Positive-sense viral RNA is similar to

mRNA In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of Protein biosynthesis, synthesizing a protein. mRNA is ...

and thus can be immediately translated by the host cell. Negative-sense viral RNA is complementary to mRNA and thus must be converted to positive-sense RNA by an

RNA-dependent RNA polymerase RNA-dependent RNA polymerase (RdRp) or RNA replicase is an enzyme that catalyzes the self-replication, replication of RNA from an RNA template. Specifically, it catalyzes synthesis of the RNA strand Complementarity (molecular biology), compleme ...

before translation. Purified RNA of a positive-sense virus can directly cause infection though it may be less infectious than the whole virus particle. In contrast, purified RNA of a negative-sense virus is not infectious by itself as it needs to be transcribed into positive-sense RNA; each

virion A virion (plural, ''viria'' or ''virions'') is an inert virus particle capable of invading a Cell (biology), cell. Upon entering the cell, the virion disassembles and the genetic material from the virus takes control of the cell infrastructure, t ...

can be transcribed to several positive-sense RNAs. Ambisense RNA viruses resemble negative-sense RNA viruses, except they translate genes from their negative and positive strands.

Double-stranded RNA viruses

The double-stranded (ds)RNA viruses represent a diverse group of viruses that vary widely in host range (humans, animals, plants,

fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

, and

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

segment number (one to twelve), and

organization ( Triangulation number,

capsid A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or m ...

layers, spikes, turrets, etc.). Members of this group include the

rotavirus Rotaviruses are the most common cause of diarrhea, diarrhoeal disease among infants and young children. Nearly every child in the world is infected with a rotavirus at least once by the age of five. Immunity (medical), Immunity develops with ...

es, which are the most common cause of

gastroenteritis Gastroenteritis, also known as infectious diarrhea, is an inflammation of the Human gastrointestinal tract, gastrointestinal tract including the stomach and intestine. Symptoms may include diarrhea, vomiting, and abdominal pain. Fever, lack of ...

in young children, and picobirnaviruses, which are the most common virus in fecal samples of both humans and animals with or without signs of diarrhea. Bluetongue virus is an economically important pathogen that infects cattle and sheep. In recent years, progress has been made in determining atomic and subnanometer resolution structures of a number of key viral proteins and virion capsids of several dsRNA viruses, highlighting the significant parallels in the structure and replicative processes of many of these viruses.

Mutation rates

RNA viruses generally have very high

mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, ...

rates compared to

DNA virus A DNA virus is a virus that has a genome made of deoxyribonucleic acid (DNA) that is replicated by a DNA polymerase. They can be divided between those that have two strands of DNA in their genome, called double-stranded DNA (dsDNA) viruses, and t ...

es, because viral

RNA polymerases In molecular biology, RNA polymerase (abbreviated RNAP or RNApol), or more specifically DNA-directed/dependent RNA polymerase (DdRP), is an enzyme that catalyzes the chemical reactions that synthesize RNA from a DNA template. Using the en ...

lack the

proofreading Proofreading is a phase in the process of publishing where galley proofs are compared against the original manuscripts or graphic artworks, to identify transcription errors in the typesetting process. In the past, proofreaders would place corr ...

ability of

DNA polymerase A DNA polymerase is a member of a family of enzymes that catalyze the synthesis of DNA molecules from nucleoside triphosphates, the molecular precursors of DNA. These enzymes are essential for DNA replication and usually work in groups to create t ...

s. The

genetic diversity Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species. It ranges widely, from the number of species to differences within species, and can be correlated to the span of survival for a species. It is d ...

of RNA viruses is one reason why it is difficult to make effective

vaccines A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease. The safety and effectiveness of vaccines has been widely studied and verified. A vaccine typically contains an ag ...

against them. Retroviruses also have a high mutation rate even though their DNA intermediate integrates into the host genome (and is thus subject to host DNA proofreading once integrated), because errors during reverse transcription are embedded into both strands of DNA before integration. Some genes of RNA virus are important to the viral replication cycles and mutations are not tolerated. For example, the region of the

hepatitis C virus The hepatitis C virus (HCV) is a small (55–65 nm in size), enveloped, positive-sense single-stranded RNA virus of the family ''Flaviviridae''. The hepatitis C virus is the cause of hepatitis C and some cancers such as liver cancer ( hepatoc ...

genome that encodes the core protein is highly conserved, because it contains an RNA structure involved in an

internal ribosome entry site An internal ribosome entry site, abbreviated IRES, is an RNA element that allows for translation initiation in a cap-independent manner, as part of the greater process of protein synthesis. Initiation of eukaryotic translation nearly always occur ...

Sequence complexity

On average, dsRNA viruses show a lower sequence redundancy relative to ssRNA viruses. Contrarily, dsDNA viruses contain the most redundant genome sequences while ssDNA viruses have the least. The sequence complexity of viruses has been shown to be a key characteristic for accurate reference-free viral classification.

Replication

There are three distinct groups of RNA viruses depending on their genome and mode of replication: * Double-stranded RNA viruses (Group III) contain from one to a dozen different RNA molecules, each coding for one or more viral proteins. * Positive-sense ssRNA viruses (Group IV) have their genome directly utilized as mRNA, with host

ribosomes Ribosomes () are macromolecular machines, found within all cells, that perform biological protein synthesis (messenger RNA translation). Ribosomes link amino acids together in the order specified by the codons of messenger RNA molecules to fo ...

translating it into a single protein that is modified by host and viral proteins to form the various proteins needed for replication. One of these includes RNA-dependent RNA polymerase (RNA replicase), which copies the viral RNA to form a double-stranded replicative form. In turn, this dsRNA directs the formation of new viral RNA. * Negative-sense ssRNA viruses (Group V) must have their genome copied by an RNA replicase to form positive-sense RNA. This means that the virus must bring along with it the enzyme RNA replicase. The positive-sense RNA molecule then acts as viral mRNA, which is translated into proteins by the host ribosomes.

Retrovirus A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. After invading a host cell's cytoplasm, the virus uses its own reverse transcriptase e ...

es (Group VI) have a single-stranded RNA genome but, in general, are not considered RNA viruses because they use DNA intermediates to replicate.

Reverse transcriptase A reverse transcriptase (RT) is an enzyme used to convert RNA genome to DNA, a process termed reverse transcription. Reverse transcriptases are used by viruses such as HIV and hepatitis B to replicate their genomes, by retrotransposon mobi ...

, a viral enzyme that comes from the virus itself after it is uncoated, converts the viral RNA into a complementary strand of DNA, which is copied to produce a double-stranded molecule of viral DNA. After this DNA is integrated into the host genome using the viral enzyme

integrase Retroviral integrase (IN) is an enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme ...

, expression of the encoded genes may lead to the formation of new virions.

Recombination

Numerous RNA viruses are capable of

genetic recombination Genetic recombination (also known as genetic reshuffling) is the exchange of genetic material between different organisms which leads to production of offspring with combinations of traits that differ from those found in either parent. In eukaryot ...

when at least two viral

s are present in the same host cell. Very rarely viral RNA can recombine with host RNA. RNA recombination appears to be a major driving force in determining genome architecture and the course of viral evolution among ''

Picornaviridae Picornaviruses are a group of related nonenveloped RNA viruses which infect vertebrates including fish, mammals, and birds. They are viruses that represent a large family of small, positive-sense, single-stranded RNA viruses with a 30 nm ...

'' ( (+)ssRNA), e.g.

poliovirus Poliovirus, the causative agent of polio (also known as poliomyelitis), is a serotype of the species '' Enterovirus C'', in the family of '' Picornaviridae''. There are three poliovirus serotypes, numbered 1, 2, and 3. Poliovirus is composed ...

. In the ''

Retroviridae A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. After invading a host cell's cytoplasm, the virus uses its own reverse transcriptase ...

'' ((+)ssRNA), e.g.

HIV The human immunodeficiency viruses (HIV) are two species of '' Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the im ...

, damage in the RNA genome appears to be avoided during

reverse transcription A reverse transcriptase (RT) is an enzyme used to convert RNA genome to DNA, a process termed reverse transcription. Reverse transcriptases are used by viruses such as HIV and hepatitis B virus, hepatitis B to replicate their genomes, by retrot ...

by strand switching, a form of recombination. Recombination also occurs in the ''

Reoviridae ''Reovirales'' is an order of double-stranded RNA viruses. Member viruses, called reoviruses, have a wide host range, including vertebrates, invertebrates, plants, protists and fungi. They lack lipid envelopes and package their segmented geno ...

'' (dsRNA), e.g. reovirus; ''

Orthomyxoviridae ''Orthomyxoviridae'' () is a family of negative-sense single-stranded RNA virus, negative-sense RNA viruses. It includes nine genus, genera: ''Influenza A virus, Alphainfluenzavirus'', ''Influenza B virus, Betainfluenzavirus'', ''Influenza C vir ...

'' ((-)ssRNA), e.g.

influenza virus ''Orthomyxoviridae'' () is a family of negative-sense RNA viruses. It includes nine genera: '' Alphainfluenzavirus'', '' Betainfluenzavirus'', '' Gammainfluenzavirus'', '' Deltainfluenzavirus'', '' Isavirus'', '' Mykissvirus'', '' Quaranjavir ...

; and ''

Coronaviridae ''Coronaviridae'' is a family (biology), family of Viral envelope, enveloped, positive-strand RNA viruses which infect fish, amphibians, birds, and mammals. The group includes the subfamilies ''Letovirinae,'' ''Orthocoronavirinae'', and ''Pitovir ...

'' ((+)ssRNA), e.g.

. Recombination in RNA viruses appears to be an adaptation for coping with genome damage. Recombination can occur infrequently between animal viruses of the same species but of divergent lineages. The resulting recombinant viruses may sometimes cause an outbreak of infection in humans.

Classification

Classification is based principally on the type of genome (double-stranded, negative- or positive-single-strand) and gene number and organization. Currently, there are 5 orders and 47 families of RNA viruses recognized. There are also many unassigned species and genera. Related to but distinct from the RNA viruses are the

viroid Viroids are small single-stranded, circular RNAs that are infectious pathogens. Unlike viruses, they have no protein coating. All known viroids are inhabitants of angiosperms (flowering plants), and most cause diseases, whose respective eco ...

s and the RNA satellite viruses. These are not currently classified as RNA viruses and are described on their own pages. A study of several thousand RNA viruses has shown the presence of at least five main taxa: a levivirus and relatives group; a picornavirus supergroup; an alphavirus supergroup plus a flavivirus supergroup; the dsRNA viruses; and the -ve strand viruses. The

lentivirus ''Lentivirus'' is a genus of retroviruses that cause chronic and deadly diseases characterized by long incubation periods, in humans and other mammalian species. The genus includes the human immunodeficiency virus (HIV), which causes AIDS. Lent ...

group appears to be basal to all the remaining RNA viruses. The next major division lies between the picornasupragroup and the remaining viruses. The dsRNA viruses appear to have evolved from a +ve RNA ancestor and the -ve RNA viruses from within the dsRNA viruses. The closest relation to the -ve stranded RNA viruses is the

Positive-strand RNA viruses

This is the single largest group of RNA viruses and has been organized by the ICTV into the phyla '' Kitrinoviricota'', '' Lenarviricota'', and '' Pisuviricota'' in the kingdom '' Orthornavirae'' and

realm A realm is a community or territory over which a sovereign rules. The term is commonly used to describe a monarchical or dynastic state. A realm may also be a subdivision within an empire, if it has its own monarch, e.g. the German Empire. Etymo ...

''. Positive-strand RNA viruses can also be classified based on the RNA-dependent RNA polymerase. Three groups have been recognised: # Bymoviruses, comoviruses, nepoviruses, nodaviruses, picornaviruses, potyviruses, sobemoviruses and a subset of luteoviruses (beet western yellows virus and potato leafroll virus)—the picorna like group (Picornavirata). # Carmoviruses, dianthoviruses, flaviviruses, pestiviruses, statoviruses, tombusviruses, single-stranded RNA bacteriophages, hepatitis C virus and a subset of luteoviruses (barley yellow dwarf virus)—the flavi like group (Flavivirata). # Alphaviruses, carlaviruses, furoviruses, hordeiviruses, potexviruses, rubiviruses, tobraviruses, tricornaviruses, tymoviruses, apple chlorotic leaf spot virus, beet yellows virus and hepatitis E virus—the alpha like group (Rubivirata). A division of the alpha-like (Sindbis-like) supergroup on the basis of a novel domain located near the N termini of the proteins involved in viral replication has been proposed. The two groups proposed are: the 'altovirus' group (alphaviruses, furoviruses, hepatitis E virus, hordeiviruses, tobamoviruses, tobraviruses, tricornaviruses and probably rubiviruses); and the 'typovirus' group (apple chlorotic leaf spot virus, carlaviruses, potexviruses and tymoviruses). The alpha like supergroup can be further divided into three

clades In biology, a clade (), also known as a monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach to taxonomy ...

: the rubi-like, tobamo-like, and tymo-like viruses. Additional work has identified five groups of positive-stranded RNA viruses containing four, three, three, three, and one order(s), respectively. These fourteen orders contain 31 virus families (including 17 families of plant viruses) and 48 genera (including 30 genera of plant viruses). This analysis suggests that alphaviruses and flaviviruses can be separated into two families—the Togaviridae and Flaviridae, respectively—but suggests that other taxonomic assignments, such as the pestiviruses, hepatitis C virus, rubiviruses, hepatitis E virus, and arteriviruses, may be incorrect. The coronaviruses and toroviruses appear to be distinct families in distinct orders and not distinct genera of the same family as currently classified. The luteoviruses appear to be two families rather than one, and apple chlorotic leaf spot virus appears not to be a closterovirus but a new genus of the Potexviridae.

Evolution

The evolution of the picornaviruses based on an analysis of their RNA polymerases and

helicase Helicases are a class of enzymes that are vital to all organisms. Their main function is to unpack an organism's genetic material. Helicases are motor proteins that move directionally along a nucleic double helix, separating the two hybridized ...

s appears to date to the divergence of

eukaryote The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

s. Their putative ancestors include the bacterial group II

retroelement Retrotransposons (also called Class I transposable elements) are transposable element, mobile elements which move in the host genome by converting their transcribed RNA into DNA through reverse transcription. Thus, they differ from Class II trans ...

s, the family of HtrA

protease A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalysis, catalyzes proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the formation of new protein products ...

s and DNA

bacteriophage A bacteriophage (), also known informally as a phage (), is a virus that infects and replicates within bacteria. The term is derived . Bacteriophages are composed of proteins that Capsid, encapsulate a DNA or RNA genome, and may have structu ...

s. Partitiviruses are related to and may have evolved from a totivirus ancestor. Hypoviruses and barnaviruses appear to share an ancestry with the potyvirus and sobemovirus lineages respectively.

Double-stranded RNA viruses

This analysis also suggests that the dsRNA viruses are not closely related to each other but instead belong to four additional classes—Birnaviridae, Cystoviridae, Partitiviridae, and Reoviridae—and one additional order (Totiviridae) of one of the classes of positive ssRNA viruses in the same subphylum as the positive-strand RNA viruses. One study has suggested that there are two large clades: One includes the families ''Caliciviridae'', ''Flaviviridae'', and ''Picornaviridae'' and a second that includes the families ''Alphatetraviridae'', ''Birnaviridae'', ''Cystoviridae'', ''Nodaviridae'', and ''Permutotretraviridae''.

Negative strand RNA viruses

These viruses have multiple types of genome ranging from a single RNA molecule up to eight segments. Despite their diversity it appears that they may have originated in

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

s and to have diversified from there.

Satellite viruses

A number of satellite viruses—viruses that require the assistance of another virus to complete their life cycle—are also known. Their taxonomy has yet to be settled. The following four genera have been proposed for positive sense single stranded RNA satellite viruses that infect plants— Albetovirus, Aumaivirus, Papanivirus and Virtovirus. A family— Sarthroviridae which includes the genus Macronovirus—has been proposed for the positive sense single stranded RNA satellite viruses that infect

Group III – dsRNA viruses

There are twelve families and a number of unassigned genera and species recognised in this group. * Family Amalgaviridae * Family Birnaviridae * Family Chrysoviridae * Family Cystoviridae * Family

Endornaviridae ''Endornaviridae'' is a family of viruses. Plants, fungi, and oomycetes serve as natural hosts. There are 31 species in this family, assigned to 2 genera (''Alphaendornavirus'' and ''Betaendornavirus''). Members of ''Alphaendornavirus'' infect p ...

* Family

Hypoviridae Hypoviruses are a family of virus A virus is a submicroscopic infectious agent that replicates only inside the living Cell (biology), cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, includi ...

* Family Megabirnaviridae * Family Partitiviridae * Family Picobirnaviridae * Family

– includes

Rotavirus Rotaviruses are the most common cause of diarrhea, diarrhoeal disease among infants and young children. Nearly every child in the world is infected with a rotavirus at least once by the age of five. Immunity (medical), Immunity develops with ...

* Family

Totiviridae ''Totivirus'' is a genus of double-stranded RNA viruses in the family ''Orthototiviridae''. Fungi serve as natural hosts. The name of the group derives from Latin ''toti'' which means undivided or whole. There are 32 species in this genus. Stru ...

* Family Quadriviridae * Genus Botybirnavirus * Unassigned species ** '' Botrytis porri RNA virus 1'' ** '' Circulifer tenellus virus 1'' ** '' Colletotrichum camelliae filamentous virus 1'' ** '' Cucurbit yellows associated virus'' ** '' Sclerotinia sclerotiorum debilitation-associated virus'' ** '' Spissistilus festinus virus 1''

Group IV – positive-sense ssRNA viruses

There are three orders and 34 families recognised in this group. In addition, there are a number of unclassified species and genera. * Order

Nidovirales ''Nidovirales'' is an order of Viral envelope, enveloped, positive-strand RNA viruses which infect vertebrates and invertebrates. Host organisms include mammals, birds, reptiles, amphibians, fish, arthropods, Mollusca, molluscs, and helminths. Th ...

** Family Arteriviridae ** Family

– includes Human coronavirus (common cold viruses HCoV-229E, HCoV-HKU1, HCoV-NL63, and HCoV-OC43), MERS-CoV,

SARS-CoV-1 Severe acute respiratory syndrome coronavirus 1 (SARS-CoV-1), previously known as severe acute respiratory syndrome coronavirus (SARS-CoV), is a strain (biology), strain of coronavirus that causes severe acute respiratory syndrome (SARS), the ...

and

SARS-CoV-2 Severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) is a strain of coronavirus that causes COVID-19, the respiratory illness responsible for the COVID-19 pandemic. The virus previously had the Novel coronavirus, provisional nam ...

** Family Mesoniviridae ** Family Roniviridae * Order Picornavirales ** Family Dicistroviridae ** Family Iflaviridae ** Family Marnaviridae ** Family

– includes

Poliovirus Poliovirus, the causative agent of polio (also known as poliomyelitis), is a serotype of the species '' Enterovirus C'', in the family of '' Picornaviridae''. There are three poliovirus serotypes, numbered 1, 2, and 3. Poliovirus is composed ...

Rhinovirus The rhinovirus (from the "nose", , romanized: "of the nose", and the ) is a Positive-sense single stranded RNA virus, positive-sense, single-stranded RNA virus belonging to the genus ''Enterovirus'' in the family ''Picornaviridae''. Rhinoviru ...

(a common cold virus),

Hepatitis A Hepatitis A is an infectious liver disease caused by Hepatitis A virus (HAV); it is a type of viral hepatitis. Many cases have few or no symptoms, especially in the young. The time between infection and symptoms, in those who develop them, is ...

virus ** Family Secoviridae includes subfamily Comovirinae ** Genus Bacillariornavirus ** Species Kelp fly virus * Order Tymovirales ** Family

Alphaflexiviridae ''Alphaflexiviridae'' is a family of viruses in the order ''Tymovirales''. Plants and fungi serve as natural hosts. There are 65 species in this family, assigned to six genera. Diseases associated with this family include: mosaic and ringspot sy ...

** Family Betaflexiviridae ** Family Gammaflexiviridae ** Family Tymoviridae * Unassigned ** Family Alphatetraviridae ** Family Alvernaviridae ** Family Astroviridae ** Family Barnaviridae ** Family Benyviridae ** Family Botourmiaviridae ** Family

Bromoviridae ''Bromoviridae'' is a family of viruses A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bac ...

** Family

Caliciviridae The ''Caliciviridae'' are a family of "small round structured" viruses, members of Class IV of the Baltimore scheme. Caliciviridae bear resemblance to enlarged picornavirus and was formerly a separate genus within the picornaviridae. They are ...

– includes Norwalk virus ** Family Carmotetraviridae ** Family

Closteroviridae ''Closteroviridae'' is a family of viruses. Plants serve as natural hosts. There are seven genera in this family. Diseases associated with this family include: yellowing and necrosis, particularly affecting the phloem. Taxonomy Genome type and ...

** Family

Flaviviridae ''Flaviviridae'' is a family of Viral envelope, enveloped positive-strand RNA viruses which mainly infect mammals and birds. They are primarily spread through arthropod vector (epidemiology), vectors (mainly ticks and mosquitoes). The family gets ...

– includes Yellow fever virus,

West Nile virus West Nile virus (WNV) is a single-stranded RNA virus that causes West Nile fever. It is a member of the family ''Flaviviridae'', from the genus ''Flavivirus'', which also contains the Zika virus, dengue virus, and yellow fever virus. The virus ...

Hepatitis C virus The hepatitis C virus (HCV) is a small (55–65 nm in size), enveloped, positive-sense single-stranded RNA virus of the family ''Flaviviridae''. The hepatitis C virus is the cause of hepatitis C and some cancers such as liver cancer ( hepatoc ...

Dengue fever Dengue fever is a mosquito-borne disease caused by dengue virus, prevalent in tropical and subtropical areas. Asymptomatic infections are uncommon, mild cases happen frequently; if symptoms appear, they typically begin 3 to 14 days after i ...

virus,

Zika virus Zika virus (ZIKV; pronounced or ) is a member of the virus family ''Flaviviridae''. It is spread by daytime-active ''Aedes'' mosquitoes, such as '' A. aegypti'' and '' A. albopictus''. Its name comes from the Ziika Forest of Uganda, where ...

** Family Fusariviridae ** Family Hepeviridae ** Family

** Family Leviviridae ** Family Luteoviridae – includes Barley yellow dwarf virus ** Family Polycipiviridae ** Family Narnaviridae ** Family Nodaviridae ** Family

Permutotetraviridae ''Permutotetraviridae'' is a family of viruses. Lepidopteran insects serve as natural hosts. The family contains one genus that has two species. Diseases associated with this family include: infection outcome varies from unapparent to lethal. ...

** Family

Potyviridae ''Potyviridae'' is a family of positive-strand RNA viruses that encompasses more than 30% of known plant viruses, many of which are of great agricultural significance. The family contains 13 genera that contain 259 species. Structure Potyviri ...

** Family Sarthroviridae ** Family Statovirus ** Family

Togaviridae {{Commonscat, Viruses by family This category is for articles about virus families (or redirects to such articles). There should be no subcategories. families Families (biology) ...

– includes

Rubella Rubella, also known as German measles or three-day measles, is an infection caused by the rubella virus. This disease is often mild, with half of people not realizing that they are infected. A rash may start around two weeks after exposure and ...

Wuhan large pig roundworm virus Wuhan; is the capital of Hubei, China. With a population of over eleven million, it is the most populous city in Hubei and the List of cities in China by population, eighth-most-populous city in China. It is also one of the nine National cent ...

Satellite viruses * Family Sarthroviridae * Genus Albetovirus * Genus Aumaivirus * Genus Papanivirus * Genus Virtovirus * Chronic bee paralysis virus An unclassified astrovirus/hepevirus-like virus has also been described.Pankovics P, Boros Á, Kiss T, Engelmann P, Reuter G (2019) Genetically highly divergent RNA virus with astrovirus-like (5'-end) and hepevirus-like (3'-end) genome organization in carnivorous birds, European roller (''Coracias garrulus''). Infect Genet Evol

Group V – negative-sense ssRNA viruses

With the exception of the

Hepatitis D virus Hepatitis D is a type of viral hepatitis caused by the hepatitis delta virus (HDV). HDV is one of five known hepatitis viruses: A, B, C, D, and E. HDV is considered to be a satellite (a type of subviral agent) because it can propagate only in ...

, this group of viruses has been placed into a single phylum— Negarnaviricota. This phylum has been divided into two subphyla— Haploviricotina and Polyploviricotina. Within the subphylum Haploviricotina four classes are currently recognised: Chunqiuviricetes, Milneviricetes, Monjiviricetes and Yunchangviricetes. In the subphylum Polyploviricotina two classes are recognised: Ellioviricetes and Insthoviricetes. Six classes, seven orders and twenty four families are currently recognized in this group. A number of unassigned species and genera are yet to be classified. * Phylum '' Negarnaviricota'' ** Subphylum '' Haploviricotina'' *** Class '' Chunqiuviricetes'' **** Order '' Muvirales'' ***** Family '' Qinviridae'' *** Class '' Milneviricetes'' **** Order '' Serpentovirales'' ***** Family '' Aspiviridae'' *** Class '' Monjiviricetes'' **** Order '' Jingchuvirales'' ***** Family '' Chuviridae'' **** Order ''

Mononegavirales ''Mononegavirales'' is an order of negative-strand RNA viruses which have nonsegmented genomes. Some members that cause human disease in this order include Ebola virus, human respiratory syncytial virus, measles virus, mumps virus, Nipah viru ...

'' ***** Family ''

Bornaviridae ''Bornaviridae'' is a family of negative-strand RNA viruses in the order ''Mononegavirales''. Horses, sheep, cattle, rodents, birds, reptiles, and humans serve as natural hosts. Diseases associated with bornaviruses include Borna disease, a fata ...

'' – Borna disease virus ***** Family ''

Filoviridae ''Filoviridae'' () is a International Committee on Taxonomy of Viruses, family of RNA virus#Group_V_–_negative-sense_ssRNA_viruses, single-stranded negative-sense RNA viruses in the order (biology), order ''Mononegavirales''. Two members of the ...

'' – includes

Ebola Ebola, also known as Ebola virus disease (EVD) and Ebola hemorrhagic fever (EHF), is a viral hemorrhagic fever in humans and other primates, caused by ebolaviruses. Symptoms typically start anywhere between two days and three weeks after in ...

virus,

Marburg virus Marburg virus (MARV) is a hemorrhagic fever virus of the '' Filoviridae'' family of viruses and a member of the species '' Marburg marburgvirus'', genus '' Marburgvirus''. It causes Marburg virus disease in primates, a form of viral hemorrhag ...

***** Family '' Mymonaviridae'' ***** Family '' Nyamiviridae'' ***** Family ''

Paramyxoviridae ''Paramyxoviridae'' (from Ancient Greek, Greek ''para-'' “by the side of” and ''myxa'' “mucus”) is a family of negative-strand RNA viruses in the order ''Mononegavirales''. Vertebrates serve as natural hosts. Diseases associated with this ...

'' – includes

Measles Measles (probably from Middle Dutch or Middle High German ''masel(e)'', meaning "blemish, blood blister") is a highly contagious, Vaccine-preventable diseases, vaccine-preventable infectious disease caused by Measles morbillivirus, measles v ...

virus, Mumps virus,

Nipah virus Nipah virus (''Henipavirus nipahense'') is a bat-borne, Zoonosis, zoonotic virus that causes Nipah virus infection in humans and other animals, a disease with a very high mortality rate (40-75%). Numerous disease outbreaks caused by Nipah virus ...

, Hendra virus, and NDV ***** Family '' Pneumoviridae'' – includes RSV and

Metapneumovirus ''Metapneumovirus'' is a genus of viruses in the family ''Pneumoviridae''. Taxonomy The genus contains the following two species, listed by scientific name and followed by the exemplar virus of the species: * ''Metapneumovirus avis'', Avian metap ...

***** Family ''

Rhabdoviridae ''Rhabdoviridae'' is a family of negative-strand RNA viruses in the order ''Mononegavirales''. Vertebrates (including mammals and humans), invertebrates, plants, fungi and protozoans serve as natural hosts. Diseases associated with member virus ...

'' – includes

Rabies Rabies is a viral disease that causes encephalitis in humans and other mammals. It was historically referred to as hydrophobia ("fear of water") because its victims panic when offered liquids to drink. Early symptoms can include fever and abn ...

virus ***** Family '' Sunviridae'' ***** Genus Anphevirus ***** Genus Arlivirus ***** Genus Chengtivirus ***** Genus Crustavirus ***** Genus Wastrivirus *** Class '' Yunchangviricetes'' **** Order '' Goujianvirales'' ***** Family '' Yueviridae'' ** Subphylum '' Polyploviricotina'' *** Class '' Ellioviricetes'' **** Order ''

Bunyavirales ''Bunyaviricetes'' is a class of segmented negative-strand RNA viruses with mainly tripartite genomes. Member viruses infect arthropods, plants, protozoans, and vertebrates. The name ''Bunyaviricetes'' derives from Bunyamwera, where the virus Bun ...

'' ***** Family '' Arenaviridae'' – includes

Lassa virus Lassa virus (LASV) is an Arenaviridae, arenavirus that causes Lassa hemorrhagic fever, a type of viral hemorrhagic fever (VHF), in humans and other primates. Lassa virus is an Emerging infectious disease, emerging virus and a select agent, requi ...

***** Family '' Cruliviridae'' ***** Family '' Feraviridae'' ***** Family '' Fimoviridae'' ***** Family ''

Hantaviridae ''Hantaviridae'' is a family of viruses in the order ''Bunyavirales''. It is named for the Hantan River area in South Korea South Korea, officially the Republic of Korea (ROK), is a country in East Asia. It constitutes the southern half o ...

'' ***** Family '' Jonviridae'' ***** Family '' Nairoviridae'' ***** Family ''

Peribunyaviridae ''Peribunyaviridae'' is a Family (biology), family of viruses in the order ''Elliovirales''. Its name partially derives from Bunyamwera, Uganda, where the founding species was first isolated. Taxonomy The family contains the following genera: * ...

'' ***** Family '' Phasmaviridae'' ***** Family ''

Phenuiviridae ''Phenuiviridae'' is a family of negative-strand RNA viruses in the order '' Hareavirales''. Ruminants, camels, humans, and mosquitoes serve as natural hosts. Virology Structure Members of ''Phenuiviridae are'' enveloped viruses with hel ...

'' ***** Family ''

Tospoviridae ''Orthotospovirus'' is a genus of Negative-strand RNA virus, negative-strand RNA viruses, in the family ''Tospoviridae'' of the order ''Elliovirales,'' which infects plants. Tospoviruses take their name from the species Tomato spotted wilt virus ( ...

'' ***** Genus '' Tilapineviridae'' *** Class '' Insthoviricetes'' **** Order '' Articulavirales'' ***** Family '' Amnoonviridae'' – includes Taastrup virus ***** Family ''

'' – includes

Influenza Influenza, commonly known as the flu, is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These sympto ...

viruses * Unassigned genera: ** Genus '' Deltavirus'' – includes

Hepatitis D Hepatitis D is a type of viral hepatitis caused by the hepatitis delta virus (HDV). HDV is one of five known hepatitis viruses: A, B, C, D, and E. HDV is considered to be a satellite (a type of subviral agent) because it can propagate only in ...

virus (not a true virus, but a

subviral agent Virus classification is the process of naming viruses 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 characteri ...

)

Gallery

File:Lassa virus.JPG,

('' Arenaviridae'') File:Lymphocytic choriomeningitis virus.jpg, Lymphocytic choriomeningitis virus ('' Arenaviridae'') File:Sin Nombre virus Hanta TEM 1137 lores.jpg,

Hantavirus ''Orthohantavirus'' is a genus of viruses that includes all hantaviruses (family ''Hantaviridae'') that cause disease in humans. Orthohantaviruses, hereafter referred to as hantaviruses, are naturally found primarily in rodents. In general, each ...

(''

Bunyaviridae ''Bunyaviricetes'' is a class of segmented negative-strand RNA viruses with mainly tripartite genomes. Member viruses infect arthropods, plants, protozoans, and vertebrates. The name ''Bunyaviricetes'' derives from Bunyamwera, where the virus B ...

'') File:Marburg virus.jpg,

(''

'') File:Ebola virions.png,

Ebola virus ''Orthoebolavirus zairense'' or Zaire ebolavirus, more commonly known as Ebola virus (; EBOV), is one of six known species within the genus ''Ebolavirus''. Four of the six known ebolaviruses, including EBOV, cause a severe and often fatal vira ...

(''

'') File:Influenza virus particle 8430 lores.jpg,

(''

'') File:Measles virus.JPG,

(''

'') File:Mumps virus, negative stained TEM 8758 lores.jpg, Mumps virus (''

'') File:Respiratory Syncytial Virus (RSV) EM PHIL 2175 lores.jpg,

Human respiratory syncytial virus Respiratory syncytial virus (RSV), also called human respiratory syncytial virus (hRSV) and human orthopneumovirus, is a virus that causes infections of the respiratory tract. It is a negative-sense, single-stranded RNA virus. Its name is deriv ...

(''

'') File:Parainfluenza virus TEM PHIL 271 lores.jpg, Parainfluenza (''

'') File:Rabies Virus EM PHIL 1876.JPG,

(''

'') File:Vesicular stomatitis virus (VSV) EM 18 lores.jpg, Vesicular stomatitis virus (''

Characteristics

Single-stranded RNA viruses and RNA Sense

Double-stranded RNA viruses

Mutation rates

Sequence complexity

Replication

Recombination

Classification

Positive-strand RNA viruses

Evolution

Double-stranded RNA viruses

Negative strand RNA viruses

Satellite viruses

Group III – dsRNA viruses

Group IV – positive-sense ssRNA viruses

Group V – negative-sense ssRNA viruses

Gallery

See also

Notes

References

External links