HOME

TheInfoList




An RNA virus is a
virus A virus is a submicroscopic infectious agent In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecu ...

virus
which has ribonucleic acid (
RNA Ribonucleic acid (RNA) is a polymer A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-mer, -mer'', "part") is a Chemical substance, substance or material consisting of very large molecules, or macromolecules, composed of many Re ...

RNA
) as its genetic material. The
nucleic acid Nucleic acids are biopolymers, macromolecules, essential to all Organism, known forms of life. They are composed of nucleotides, which are the monomers made of three components: a pentose, 5-carbon sugar, a phosphate group and a nitrogenous base. ...

nucleic acid
is usually
single-stranded When referring to Transcription (genetics), DNA transcription, the coding strand is the DNA strand whose Nucleobase, base sequence is identical to the base sequence of the RNA transcript produced (although with thymine replaced by uracil). It is th ...
RNA (
ssRNA Ribonucleic acid (RNA) is a polymer A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-mer, -mer'', "part") is a Chemical substance, substance or material consisting of very large molecules, or macromolecules, composed of many Re ...
) but it may be double-stranded (dsRNA). Notable human diseases caused by RNA viruses include the common cold,
influenza Influenza, commonly known as "the flu", is an infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction of host (biology), ...

influenza
,
SARS Severe acute respiratory syndrome (SARS) is a viral respiratory disease Respiratory diseases, or lung diseases, are pathological conditions affecting the organs and tissues that make gas exchange Gas exchange is the physical process by which ga ...
,
MERS Mers may refer to: * MERS Mers may refer to: * MERS, Middle East respiratory syndrome ** Middle East respiratory syndrome–related coronavirus (MERS-CoV), the virus that causes MERS * El Mers, a town in Morocco * Mer (community) or Maher communi ...

MERS
,
COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease A contagious disease is a disease A disease is a particular abnormal condition that negatively affects the structure A structure is an arrangement and organization o ...
,
Dengue Virus ''Dengue virus'' (DENV) is the cause of dengue fever Dengue fever is a mosquito-borne tropical disease caused by the dengue virus. Symptoms typically begin three to fourteen days after infection. These may include a high fever Fever, ...
,
hepatitis C Hepatitis C is an infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction of host (biology), host tissues to the infectious ag ...

hepatitis C
,
hepatitis E Hepatitis E is inflammation of the liver caused by infection An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction of host (biology), host tissu ...
,
West Nile fever West Nile fever is an infection by the West Nile virus, which is typically spread by mosquitoes. In about 80% of infections people have Subclinical infection, few or Asymptomatic, no symptoms. About 20% of people develop a fever, headache, vomiti ...
,
Ebola virus disease Ebola, also known as Ebola virus disease (EVD) and Ebola hemorrhagic fever (EHF), is a viral hemorrhagic fever Viral hemorrhagic fevers (VHFs) are a diverse group of animal and human illness A disease is a particular abnormal co ...
,
rabies Rabies is a viral disease A viral disease (or viral infection) occurs when an organism's body is invaded by pathogenic viruses, and infection, infectious virus particles (virions) attach to and enter susceptible cells. Structural characteri ...
,
polio Poliomyelitis, commonly shortened to polio, is an infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction of host (biology) ...

polio
,
mumps Mumps is a viral disease A viral disease (or viral infection) occurs when an organism's body is invaded by pathogenic viruses, and infection, infectious virus particles (virions) attach to and enter susceptible cells. Structural characterist ...

mumps
, and
measles Measles is a highly contagious infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction of host (biology), host tissues to ...
. The
International Committee on Taxonomy of Viruses The International Committee on Taxonomy of Viruses (ICTV) authorizes and organizes the taxonomic Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification ...
(ICTV) classifies RNA viruses as those that belong to ''Group III'', ''Group IV'' or ''Group V'' of the
Baltimore classification 350px, An illustration of the "pathways" each Baltimore groups goes through to synthesize mRNA. Baltimore classification is a system used to classify virus A virus is a submicroscopic infectious agent that Viral replication, replicates o ...

Baltimore classification
system. This category excludes ''Group VI'', viruses with RNA genetic material but which use
DNA Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral gro ...

DNA
intermediates in their
life cycle Life cycle, life-cycle, or lifecycle may refer to: Science and academia *Biological life cycle, the sequence of life stages that an organism undergoes from birth to reproduction ending with the production of the offspring *Life-cycle hypothesis, ...
: these are called
retrovirus A retrovirus is a type of virus that inserts a copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. Once inside the host cell's cytoplasm, the virus uses its own reverse transcriptase enzyme ...

retrovirus
es, including
HIV-1 One of the obstacles to treatment of the human immunodeficiency virus The human immunodeficiency viruses (HIV) are two species of ''Lentivirus ''Lentivirus'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) ...
and
HIV-2 One of the obstacles to treatment of the human immunodeficiency virus (HIV) is its high genetic variability. HIV can be divided into two major types, HIV type 1 (HIV-1) and HIV type 2 (HIV-2). HIV-1 is related to viruses found in chimpanzees and g ...
which cause
AIDS Human immunodeficiency virus infection and acquired immunodeficiency syndrome (HIV/AIDS) is a spectrum of conditions caused by infection An infection is the invasion of an organism's body by , their multiplication, and the reaction of ...
As of May 2020, all known RNA viruses encoding an RNA-directed RNA polymerase are believed to form a monophyletic group, known as the realm ''
Riboviria ''Riboviria'' is a realm A realm is a community or territory over which a Sovereignty, sovereign rules. The term is commonly used to describe a Monarchy, monarchical or Dynasty, dynastic state. A realm may also be a subdivision within an empir ...
''. The majority of such RNA viruses fall into the kingdom ''
Orthornavirae ''Orthornavirae'' is a kingdom of viruses that have genomes made of ribonucleic acid (RNA) and which encode an RNA-dependent RNA polymerase (RdRp). The RdRp is used to transcribe the viral RNA genome into messenger RNA Image:MRNA-interaction.p ...
'' and the rest have a positioning not yet defined.TaxoPro
2019.006G
/ref> The realm does not contain all RNA viruses: ''
Deltavirus Hepatitis D is a type of viral hepatitis Viral hepatitis is liver inflammation due to a viral infection. It may present in acute form as a recent infection with relatively rapid onset, or in chronic form. The most common causes of viral hepat ...
'', '' Asunviroidae'', 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 Molecular biology is the branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, mole ...
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 i ...

mRNA
and thus can be immediately
translated Translation is the communication of the meaning of a source-language text by means of an equivalent target-language text. The English language draws a terminological distinction (which does not exist in every language) between ''transla ...
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 Enzymes () are s that act as s (biocatalysts). Catalysts accelerate . The molecules upon which enzymes may act are called , and the enzyme converts the substrates into diff ...
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 virus is a submicroscopic infectious agent In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecu ...

virion
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 (plural The plural (sometimes abbreviated An abbreviation (from Latin ''brevis'', meaning ''short'') is a shortened form of a word or phrase, by any method. It may consist of a group of letters, or words taken from the full ...

fungi
, and
bacteria Bacteria (; common noun bacteria, singular bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typ ...

bacteria
),
genome In the fields of molecular biology Molecular biology is the branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, M ...

genome
segment number (one to twelve), and
virion A virus is a submicroscopic infectious agent In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecu ...

virion
organization (
Triangulation number 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 may n ...
,
capsid A capsid is the protein shell of a virus A virus is a that only inside the living of an . Viruses infect all , from animals and plants to s, including and . Since 's 1892 article describing a non-bacterial infecting tobacco plants ...
layers, spikes, turrets, etc.). Members of this group include the
rotavirus ''Rotavirus'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), cir ...

rotavirus
es, which are the most common cause of
gastroenteritis Gastroenteritis, also known as infectious diarrhea and gastro, is inflammation of the gastrointestinal tract The gastrointestinal tract, (GI tract, GIT, digestive tract, digestion tract, alimentary canal) is the tract from the mouth to the ...

gastroenteritis
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. 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 Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechan ...
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, and officially DNA-directed (dependent) RNA polymerase), is an enzyme that synthesizes RNA from a DNA template. Using the enzyme helicase, RNAP locally opens the double-strande ...
lack the
proofreading Proofreading is the reading Reading is the process of taking in the sense or meaning of letters, symbols, etc., especially by sight or touch. For educators and researchers, reading is a multifaceted process involving such areas as word rec ...
ability of
DNA polymerase A DNA polymerase is a member of a family of enzyme Enzymes () are s that act as s (biocatalysts). Catalysts accelerate . The molecules upon which enzymes may act are called , and the enzyme converts the substrates into different molecules ...

DNA polymerase
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 In biology, a species is the basic unit of biological classificati ...
of RNA viruses is one reason why it is difficult to make effective
vaccines A vaccine is a biological preparation that provides active to a particular . A vaccine typically contains an agent that resembles a disease-causing microorganism and is often made from weakened or killed forms of the microbe, its toxins, or o ...
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 An RNA virus is a virus A virus is a submicroscopic infectious agent that Viral replication, replicates only inside ...
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 Ribonucleic acid (RNA) is a polymer A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-mer, -mer'', "part") is a Chemical substance, substance or material consisting of v ...
.


Replication

Animal RNA viruses are classified by the ICTV. 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 molecular machine, macromolecular machines, found within all living cell (biology), cells, that perform Translation (biology), biological protein synthesis (mRNA translation). Ribosomes link amino acids together in the order spec ...

ribosomes
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 A virus is a submicroscopic infectious agent In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical ...

Retrovirus
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 Enzymes () are protein Proteins are large s and s that comprise one or more long chains of . Proteins perform a vast array of functions within organisms, including , , , providing and , an ...
, 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 Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates ...
, 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 organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, ph ...
when at least two viral
genome In the fields of molecular biology Molecular biology is the branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, M ...

genome
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 Viral envelope, 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 virus, positiv ...

Picornaviridae
'' ( (+)ssRNA), e.g.
poliovirus A poliovirus, the causative agent of polio Poliomyelitis, commonly shortened to polio, is an infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multi ...
. In the ''
Retroviridae A retrovirus is a type of virus A virus is a submicroscopic infectious agent that Viral replication, replicates only inside the living Cell (biology), cells of an organism. Viruses infect all types of life forms, from animals and plant ...

Retroviridae
'' ((+)ssRNA), e.g.
HIV The human immunodeficiency viruses (HIV) are two species of ''Lentivirus ''Lentivirus'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, inc ...

HIV
, damage in the RNA genome appears to be avoided during
reverse transcription A reverse transcriptase (RT) is an enzyme Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrate ...
by strand switching, a form of recombination. Recombination also occurs in the ''
Reoviridae ''Reoviridae'' is a family In human society, family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of families is to maintain the ...
'' (dsRNA), e.g. reovirus; ''
Orthomyxoviridae ''Orthomyxoviridae'' (ὀρθός, ''orthós'', Greek for "straight"; μύξα, ''mýxa'', Greek for "mucus Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mu ...
'' ((-)ssRNA), e.g.
influenza virus ''Orthomyxoviridae'' (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population ...

influenza virus
; and ''
Coronaviridae ''Coronaviridae'' is a family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain the well-being of its members and of soc ...
'' ((+)ssRNA), e.g.
SARS Severe acute respiratory syndrome (SARS) is a viral respiratory disease Respiratory diseases, or lung diseases, are pathology, pathological conditions affecting the organs and tissues that make gas exchange difficult in Breathing, air-breathing ...
. 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 of the RNA viruses is difficult. This is in part due to the high mutation rates these genomes undergo. 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 RNA Circular RNA (or circRNA) is a type of single-stranded RNA which, unlike linear RNA, forms a covalently closed continuous loop. In circular RNA, the 3' and 5' ends normally present in an RNA mole ...
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 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
Reoviridae ''Reoviridae'' is a family In human society, family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of families is to maintain the ...
.


Positive strand RNA viruses

This is the single largest group of RNA viruses with 30 families. Attempts have been made to group these families in higher orders. These proposals were based on an analysis of the RNA polymerases and are still under consideration. To date, the suggestions proposed have not been broadly accepted because of doubts over the suitability of a single gene to determine the taxonomy of the clade. The proposed classification of positive-strand RNA viruses is 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 A clade (), also known as a monophyletic group or natural group, is a group of organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry ...
: 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 enzyme Enzymes () are protein Proteins are large s and s that comprise one or more long chains of . Proteins perform a vast array of functions within organisms, including , , , providing and , and from one ...

helicase
s appears to date to the divergence of
eukaryote Eukaryotes () are organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interact ...

eukaryote
s. Their putative ancestors include the bacterial group II retroelements, the family of HtrA
protease A protease (also called a peptidase or proteinase) is an enzyme Enzymes () are s that act as s (biocatalysts). Catalysts accelerate . The molecules upon which enzymes may act are called , and the enzyme converts the substrates into differe ...

protease
s and DNA
bacteriophage A bacteriophage (), also known informally as a ''phage'' (), is a virus A virus is a submicroscopic infectious agent In biology Biology is the natural science that studies life and living organisms, including their anatomy, ...

bacteriophage
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 An arthropod (, (gen. ποδός)) is an invertebrate animal having an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Euarthropoda,Reference showing that Euarthropoda is a phylum: ...
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
arthropod An arthropod (, (gen. ποδός)) is an invertebrate animal having an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Euarthropoda,Reference showing that Euarthropoda is a phylum: ...
s.


Group III – dsRNA viruses

There are twelve families and a number of unassigned genera and species recognised in this group. * Family
Amalgaviridae ''Amalgaviridae'' is a family of Double-stranded RNA viruses, double-stranded RNA viruses. Member viruses infect plants and are Vertical transmission, transmitted vertically via seeds. The name derives from ''amalga''m (blend, mix) which refers to ...
* Family Birnaviridae * Family Chrysoviridae * Family
Cystoviridae ''Cystovirus'' is a genus of double-stranded RNA viruses Double-stranded RNA viruses (dsRNA viruses) are a polyphyletic 300px, Cladogram of the primates, showing a monophyly (the simians, in yellow), a paraphyly">monophyly.html" ;"title="p ...
* Family Endornaviridae * Family
Hypoviridae ''Hypovirus'' is a genus of viruses, in the family ''Hypoviridae''. Fungi serve as natural hosts. There are currently four species in this genus including the type species '' Cryphonectria hypovirus 1''. Diseases associated with this genus inclu ...
* Family Megabirnaviridae * Family
Partitiviridae ''Partitiviridae'' is a family of double-stranded RNA viruses. Fungi and plants serve as natural hosts. The name comes from the Latin ''partitius,'' which means divided, and refers to the segmented genome of partitiviruses. There are 60 species ...
* Family
Picobirnaviridae ''Picobirnavirus'' is a genus of double-stranded RNA viruses. It is the only genus the family ''Picobirnaviridae''. Although amniotes, especially mammals, were thought to serve as hosts, it has been recently suggested that these viruses might in ...
* Family
Reoviridae ''Reoviridae'' is a family In human society, family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of families is to maintain the ...
 – includes
Rotavirus ''Rotavirus'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), cir ...

Rotavirus
* Family
Totiviridae ''Totiviridae'' is a family of double-stranded RNA viruses. Giardia lamblia, leishmania, trichomonas vaginalis, and fungi serve as natural hosts. The name of the group derives from Latin ''toti'' which means undivided or whole. There are currentl ...
* 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 ** Family Arteriviridae ** Family
Coronaviridae ''Coronaviridae'' is a family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain the well-being of its members and of soc ...
– includes Human coronavirus (common cold viruses Human coronavirus 229E, HCoV-229E, Human coronavirus HKU1, HCoV-HKU1, Human coronavirus NL63, HCoV-NL63, and Human coronavirus OC43, HCoV-OC43), MERS-CoV, SARS-CoV-1 and SARS-CoV-2 ** Family Mesoniviridae ** Family Roniviridae * Order Picornavirales ** Family Dicistroviridae ** Family Iflaviridae ** Family Marnaviridae ** Family Picornaviridae – includes Poliovirus, Rhinovirus (a common cold virus), Hepatitis A virus ** Family Secoviridae includes subfamily Comoviridae, Comovirinae ** Genus Bacillariornavirus ** Species Kelp fly virus * Order Tymovirales ** Family Alphaflexiviridae ** Family Betaflexiviridae ** Family Gammaflexiviridae ** Family Tymoviridae * Unassigned ** Family Alphatetraviridae ** Family Alvernaviridae ** Family Astroviridae ** Family Barnavirus, Barnaviridae ** Family Benyviridae ** Family Botourmiaviridae ** Family Bromoviridae ** Family Caliciviridae – includes Norovirus, Norwalk virus ** Family Carmotetraviridae ** Family Closteroviridae ** Family Flaviviridae – includes Yellow fever virus, West Nile virus, Hepatitis C virus, Dengue fever virus, Zika virus ** Family Fusariviridae ** Family Hepeviridae ** Family
Hypoviridae ''Hypovirus'' is a genus of viruses, in the family ''Hypoviridae''. Fungi serve as natural hosts. There are currently four species in this genus including the type species '' Cryphonectria hypovirus 1''. Diseases associated with this genus inclu ...
** Family Leviviridae ** Family Luteoviridae – includes Barley yellow dwarf virus ** Family Polycipiviridae ** Family Narnaviridae ** Family Nodaviridae ** Family Permutotetraviridae ** Family Potyviridae ** Family Sarthroviridae ** Family Statovirus ** Family Togaviridae – includes Rubella virus, Ross River virus, Sindbis virus, Chikungunya virus ** Family Tombusviridae ** Family Virgaviridae ** Unassigned genera *** Genus ''Blunervirus'' *** Genus ''Cilevirus'' *** Genus ''Higrevirus'' *** Genus ''Idaeovirus'' *** Genus ''Negevirus'' *** Genus ''Ourmiavirus'' *** Genus ''Polemovirus'' *** Genus ''Sinaivirus'' *** Genus ''Sobemovirus'' ** Unassigned species *** Acyrthosiphon pisum virus *** Bastrovirus *** Blackford virus *** Blueberry necrotic ring blotch virus *** Cadicistrovirus *** Chara australis virus *** Extra small virus *** Goji berry chlorosis virus *** Harmonia axyridis virus 1 *** Hepelivirus *** Jingmen tick virus *** Le Blanc virus *** Nedicistrovirus *** Nesidiocoris tenuis virus 1 *** Niflavirus *** Nylanderia fulva virus 1 *** Orsay virus *** Osedax japonicus RNA virus 1 *** Picalivirus *** Planarian secretory cell nidovirus *** Plasmopara halstedii virus *** Rosellinia necatrix fusarivirus 1 *** Santeuil virus *** Secalivirus *** Solenopsis invicta virus 3 *** Wuhan large pig roundworm virus 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, 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'' ***** Family ''Borna disease, Bornaviridae'' – Borna disease virus ***** Family ''Filoviridae'' – includes Ebola virus, Marburg virus ***** Family ''Mymonaviridae'' ***** Family ''Nyamiviridae ***** Family ''Paramyxoviridae'' – includes Measles virus, Mumps virus, Nipah virus, Hendra virus, and Newcastle disease, NDV ***** Family ''Pneumoviridae'' – includes Human respiratory syncytial virus, RSV and Metapneumovirus ***** Family ''Rhabdoviridae'' – includes Rabies 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'' ***** Family ''Arenaviridae'' – includes Lassa virus ***** Family ''Cruliviridae'' ***** Family ''Feraviridae'' ***** Family ''Fimoviridae'' ***** Family ''Hantaviridae'' ***** Family ''Jonviridae'' ***** Family ''Nairoviridae'' ***** Family ''Peribunyaviridae'' ***** Family ''Phasmaviridae'' ***** Family ''Phenuiviridae'' ***** Family ''Tospoviridae'' ***** Genus ''Tilapineviridae'' *** Class ''Insthoviricetes'' **** Order ''Articulavirales'' ***** Family ''Amnoonviridae'' – includes Taastrup virus ***** Family ''
Orthomyxoviridae ''Orthomyxoviridae'' (ὀρθός, ''orthós'', Greek for "straight"; μύξα, ''mýxa'', Greek for "mucus Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mu ...
'' – includes Influenza viruses * Unassigned genera: ** Genus ''
Deltavirus Hepatitis D is a type of viral hepatitis Viral hepatitis is liver inflammation due to a viral infection. It may present in acute form as a recent infection with relatively rapid onset, or in chronic form. The most common causes of viral hepat ...
'' – includes Hepatitis D virus (not a true virus, but a subviral agent)


Gallery

File:Lassa virus.JPG, Lassa virus (''Arenaviridae'') File:Lymphocytic choriomeningitis virus.jpg, Lymphocytic choriomeningitis virus (''Arenaviridae'') File:Sin Nombre virus Hanta TEM 1137 lores.jpg, Hantavirus (''Bunyaviridae'') File:Marburg virus.jpg, Marburg Virus (''Filoviridae'') File:Ebola virions.png, Ebola virus (''Filoviridae'') File:Influenza virus particle 8430 lores.jpg, Influenza (''
Orthomyxoviridae ''Orthomyxoviridae'' (ὀρθός, ''orthós'', Greek for "straight"; μύξα, ''mýxa'', Greek for "mucus Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mu ...
'') File:Measles virus.JPG, Measles (''Paramyxoviridae'') File:Mumps virus, negative stained TEM 8758 lores.jpg, Mumps virus (''Paramyxoviridae'') File:Respiratory Syncytial Virus (RSV) EM PHIL 2175 lores.jpg, Human respiratory syncytial virus (''Paramyxoviridae'') File:Parainfluenza virus TEM PHIL 271 lores.jpg, Parainfluenza (''Paramyxoviridae'') File:Rabies Virus EM PHIL 1876.JPG, Rabies (''Rhabdoviridae'') File:Vesicular stomatitis virus (VSV) EM 18 lores.jpg, Vesicular stomatitis virus (''Rhabdoviridae'')


See also

* Virus classification * List of viruses * Virus#Replication cycle, Viral replication * Sense (molecular biology), Positive/negative-sense * Animal virology, Animal viruses * Double-stranded RNA viruses *
Retrovirus A retrovirus is a type of virus A virus is a submicroscopic infectious agent In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical ...

Retrovirus
* DNA viruses * Norovirus cis-acting replication element * Viroid


Notes


References


External links

*
Animal viruses
{{Authority control RNA viruses, RNA