''Coronaviridae'' is a

family 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 the family is to maintain the well-being of its members and of society. Idea ...

of enveloped,

positive-strand RNA virus Positive-strand RNA viruses (+ssRNA viruses) are a group of related viruses that have positive-sense, single-stranded genomes made of ribonucleic acid. The positive-sense genome can act as messenger RNA (mRNA) and can be directly translated int ...

es which infect amphibians,

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

s, and mammals. The group includes the subfamilies ''

Letovirinae ''Letovirinae'' is a subfamily of viruses within the family ''Coronaviridae'', where it is the only subfamily besides the more diverse ''Orthocoronavirinae'' (coronaviruses). ''Letovirinae'' contains one accepted genus, ''Alphaletovirus'', which ...

'' and ''

Orthocoronavirinae Coronaviruses are a group of related RNA viruses that cause diseases in mammals and birds. In humans and birds, they cause respiratory tract infections that can range from mild to lethal. Mild illnesses in humans include some cases of the c ...

;'' the members of the latter are known as coronaviruses. The viral genome is 26–32

kilobase A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DN ...

s in length. The particles are typically decorated with large (~20 nm), club- or petal-shaped surface projections (the "

peplomer In virology, a spike protein or peplomer protein is a protein that forms a large structure known as a spike or peplomer projecting from the surface of an enveloped virus. as cited in The proteins are usually glycoproteins that form dimers o ...

s" or "spikes"), which in electron micrographs of spherical particles create an image reminiscent of the

solar corona A corona ( coronas or coronae) is the outermost layer of a star's atmosphere. It consists of plasma. The Sun's corona lies above the chromosphere and extends millions of kilometres into outer space. It is most easily seen during a total solar ...

Virology

The 5' and 3' ends of the genome have a

cap A cap is a flat headgear, usually with a visor. Caps have crowns that fit very close to the head. They made their first appearance as early as 3200 BC. Caps typically have a visor, or no brim at all. They are popular in casual and informal se ...

and

poly(A) tract Polyadenylation is the addition of a poly(A) tail to an RNA transcript, typically a messenger RNA (mRNA). The poly(A) tail consists of multiple adenosine monophosphates; in other words, it is a stretch of RNA that has only adenine bases. In eu ...

, respectively. The

viral envelope A viral envelope is the outermost layer of many types of viruses. It protects the genetic material in their life cycle when traveling between host cells. Not all viruses have envelopes. Numerous human pathogenic viruses in circulation are encase ...

, obtained by budding through membranes of the endoplasmic reticulum (ER) or

Golgi apparatus The Golgi apparatus (), also known as the Golgi complex, Golgi body, or simply the Golgi, is an organelle found in most eukaryotic cells. Part of the endomembrane system in the cytoplasm, it packages proteins into membrane-bound vesicles ...

, invariably contains two virus-specified glycoprotein species, known as the spike (S) and membrane (M) proteins. The

spike protein In virology, a spike protein or peplomer protein is a protein that forms a large structure known as a spike or peplomer projecting from the surface of an enveloped virus. as cited in The proteins are usually glycoproteins that form dimers or ...

makes up the large surface projections (sometimes known as

s), while the

membrane protein Membrane proteins are common proteins that are part of, or interact with, biological membranes. Membrane proteins fall into several broad categories depending on their location. Integral membrane proteins are a permanent part of a cell membrane ...

is a triple-spanning

transmembrane protein A transmembrane protein (TP) is a type of integral membrane protein that spans the entirety of the cell membrane. Many transmembrane proteins function as gateways to permit the transport of specific substances across the membrane. They frequent ...

Torovirus ''Torovirus'' is a genus of enveloped, positive-strand RNA viruses in the order '' Nidovirales'' and family '' Tobaniviridae''. They primarily infect vertebrates, especially cattle, pigs, and horses. Diseases associated with this genus include ...

es and a select subset of coronaviruses (in particular the members of subgroup A in the genus ''Betacoronavirus'') possess, in addition to the peplomers composed of S, a second type of surface projections composed of the hemagglutinin-esterase protein. Another important structural

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

is the

phosphoprotein A phosphoprotein is a protein that is posttranslationally modified by the attachment of either a single phosphate group, or a complex molecule such as 5'-phospho-DNA, through a phosphate group. The target amino acid is most often serine, threonin ...

nucleocapsid protein (N), which is responsible for the helical symmetry of the nucleocapsid that encloses the genomic RNA. The fourth and smallest

viral structural protein A viral structural protein is a viral protein that is a structural component of the mature virus. Examples include the SARS coronavirus 3a and 7a accessory proteins. Bacteriophage T4 structural proteins During assembly of the bacteriophage (pha ...

is known as the

envelope protein A viral envelope is the outermost layer of many types of viruses. It protects the genetic material in their life cycle when traveling between host cells. Not all viruses have envelopes. Numerous human pathogenic viruses in circulation are encase ...

(E), thought to be involved in

viral budding Viral shedding is the expulsion and release of virus progeny following successful reproduction during a host (biology), host cell (biology), cell infection. Once replication has been completed and the host cell is exhausted of all resources in ma ...

. Genetic recombination can occur when at least two viral

genome In the fields of molecular biology and genetics, 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 g ...

s are present in the same infected host cell. RNA recombination appears to be a major driving force in coronavirus evolution. Recombination can determine genetic variability within a CoV species, the capability of a CoV species to jump from one host to another and, infrequently, the emergence of a novel CoV.Su S, Wong G, Shi W, Liu J, Lai ACK, Zhou J, Liu W, Bi Y, Gao GF. Epidemiology, Genetic Recombination, and Pathogenesis of Coronaviruses. Trends Microbiol. 2016 Jun;24(6):490-502. DOI: 10.1016/j.tim.2016.03.003. Epub 2016 Mar 21. Review. The exact mechanism of recombination in CoVs is not known, but likely involves template switching during genome replication.

Taxonomy

The family ''Coronaviridae'' is organized in 2 sub-families, 5 genera, 26 sub-genera, and 46 species. Additional species are pending or tentative. *''Coronaviridae'' **''

'' **''

'' ***'' Alphaletovirus'' ****'' Milecovirus'' *****'' Microhyla letovirus 1''

Coronavirus

Coronavirus is the common name for ''Coronaviridae'' and ''Orthocoronavirinae'', also called ''Coronavirinae''. Coronaviruses cause diseases in mammals and birds. In humans, the viruses cause

respiratory infection Respiratory tract infections (RTIs) are infectious diseases involving the respiratory tract. An infection of this type usually is further classified as an upper respiratory tract infection (URI or URTI) or a lower respiratory tract infection (LRI ...

s. Four human coronaviruses cause typically minor symptoms of a common cold, while three are known to cause more serious illness and can be lethal:

SARS-CoV-1 Severe acute respiratory syndrome coronavirus 1 (SARS-CoV-1; or Severe acute respiratory syndrome coronavirus, SARS-CoV) is a strain of coronavirus that causes severe acute respiratory syndrome (SARS), the respiratory illness responsible for ...

, which causes

SARS Severe acute respiratory syndrome (SARS) is a viral respiratory disease of zoonotic origin caused by the severe acute respiratory syndrome coronavirus (SARS-CoV or SARS-CoV-1), the first identified strain of the SARS coronavirus species, ''seve ...

;

MERS-CoV ''Middle East respiratory syndrome–related coronavirus'' (''MERS-CoV''), or EMC/2012 ( HCoV-EMC/2012), is the virus that causes Middle East respiratory syndrome (MERS). It is a species of coronavirus which infects humans, bats, and camels. Th ...

, which causes

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. Typical symptoms include fever, cough, ...

; and

SARS-CoV-2 Severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) is a strain of coronavirus that causes COVID-19 (coronavirus disease 2019), the respiratory illness responsible for the ongoing COVID-19 pandemic. The virus previously had a ...

, which causes

COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by a virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first known case was identified in Wuhan, China, in December 2019. The disease quickly ...

. Symptoms vary in other species: in chickens, they cause an upper respiratory disease, while in cows and pigs coronaviruses cause diarrhea. Other than for SARS-CoV-2, there are no vaccines or antiviral drugs to prevent or treat human coronavirus infections. They are

enveloped virus A viral envelope is the outermost layer of many types of viruses. It protects the genetic material in their life cycle when traveling between host cells. Not all viruses have envelopes. Numerous human pathogenic viruses in circulation are encase ...

es with a positive-sense single-stranded

RNA Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...

and a nucleocapsid of helical symmetry. The

genome size Genome size is the total amount of DNA contained within one copy of a single complete genome. It is typically measured in terms of mass in picograms (trillionths (10−12) of a gram, abbreviated pg) or less frequently in daltons, or as the total ...

of coronaviruses ranges from approximately 26 to 32 kilobases, among the largest for an RNA virus (second only to a 41-kb

nidovirus ''Nidovirales'' is an order of enveloped, positive-strand RNA viruses which infect vertebrates and invertebrates. Host organisms include mammals, birds, reptiles, amphibians, fish, arthropods, molluscs, and helminths. The order includes the f ...

recently discovered in

planaria ''Planaria'' is a genus of planarians in the family Planariidae. When an individual is cut into pieces, each piece has the ability to regenerate into a fully formed individual. Description Currently the genus ''Planaria'' is defined as fres ...

''Orthocoronavirinae'' taxonomy

*''Orthocoronavirinae'' **''

Alphacoronavirus Alphacoronaviruses (Alpha-CoV) are members of the first of the four genera (''Alpha''-, '' Beta-'', '' Gamma-'', and '' Delta-'') of coronaviruses. They are positive-sense, single-stranded RNA viruses that infect mammals, including humans. They ...

'' ***'' Colacovirus'' ****'' Bat coronavirus CDPHE15'' ***'' Decacovirus'' ****'' Bat coronavirus HKU10'' ****'' Rhinolophus ferrumequinum alphacoronavirus HuB-2013'' ***'' Duvinacovirus'' ****''

Human coronavirus 229E ''Human coronavirus 229E'' (''HCoV-229E'') is a species of coronavirus which infects humans and bats. It is an enveloped, positive-sense, single-stranded RNA virus which enters its host cell by binding to the APN receptor. Along with Human c ...

'' ***''

Luchacovirus ''Luchacovirus'' is a subgenus of viruses in the genus ''Alphacoronavirus Alphacoronaviruses (Alpha-CoV) are members of the first of the four genera (''Alpha''-, '' Beta-'', '' Gamma-'', and '' Delta-'') of coronaviruses. They are positive-s ...

'' ****'' Lucheng Rn rat coronavirus'' ***'' Minacovirus'' ****'' Mink coronavirus 1'' ***'' Minunacovirus'' ****'' Miniopterus bat coronavirus 1'' ****'' Miniopterus bat coronavirus HKU8'' ***'' Myotacovirus'' ****'' Myotis ricketti alphacoronavirus Sax-2011'' ***'' Nyctacovirus'' ****'' Nyctalus velutinus alphacoronavirus SC-2013'' ****'' Pipistrellus kuhlii coronavirus 3398'' ***'' Pedacovirus'' ****''

Porcine epidemic diarrhea virus ''Porcine epidemic diarrhea virus'' (PED virus or PEDV) is a coronavirus that infects the cells lining the small intestine of a pig, causing porcine epidemic diarrhoea, a condition of severe diarrhea and dehydration. Older hogs mostly get sick ...

'' ****'' Scotophilus bat coronavirus 512'' ***'' Rhinacovirus'' ****'' Rhinolophus bat coronavirus HKU2'' ***'' Setracovirus'' ****''

Human coronavirus NL63 Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, an ...

'' ****'' NL63-related bat coronavirus strain BtKYNL63-9b'' ***'' Soracovirus'' ****'' Sorex araneus coronavirus T14'' ***'' Sunacovirus'' ****'' Suncus murinus coronavirus X74'' ***''

Tegacovirus ''Alphacoronavirus 1'' is a species of coronavirus that infects cats, dogs and pigs. It includes the virus strains feline coronavirus, canine coronavirus, and transmissible gastroenteritis virus.' It is an enveloped, positive-strand RNA vir ...

'' ****'' Alphacoronavirus 1'' **''

Betacoronavirus ''Betacoronavirus'' (β-CoVs or Beta-CoVs) is one of four genera (''Alpha''-, ''Beta-'', '' Gamma-'', and '' Delta-'') of coronaviruses. Member viruses are enveloped, positive-strand RNA viruses that infect mammals (of which humans are part). ...

'' ***''

Embecovirus ''Embecovirus'' is a subgenus of coronaviruses in the genus ''Betacoronavirus''. The viruses in this subgenus, unlike other coronaviruses, have a hemagglutinin esterase (HE) gene. The viruses in the subgenus were previously known as group 2a coro ...

'' ****''

Betacoronavirus 1 ''Betacoronavirus 1'' is a species of coronavirus which infects humans and cattle. The infecting virus is an enveloped, positive-sense, single-stranded RNA virus and is a member of the genus ''Betacoronavirus'' and subgenus ''Embecovirus.'' Li ...

'' *****''

Human coronavirus OC43 Human coronavirus OC43 (HCoV-OC43) is a member of the species '' Betacoronavirus 1'', which infects humans and cattle. The infecting coronavirus is an enveloped, positive-sense, single-stranded RNA virus that enters its host cell by binding to ...

'' ****''

China Rattus coronavirus HKU24 ''China Rattus coronavirus HKU24'' is a species of coronavirus in the genus ''Betacoronavirus ''Betacoronavirus'' (β-CoVs or Beta-CoVs) is one of four genera (''Alpha''-, ''Beta-'', '' Gamma-'', and '' Delta-'') of coronaviruses. Member vi ...

'' ****''

Human coronavirus HKU1 ''Human coronavirus HKU1'' (''HCoV-HKU1'') is a species of coronavirus in humans and animals. It causes an upper respiratory disease with symptoms of the common cold, but can advance to pneumonia and bronchiolitis. It was first discovered in Jan ...

'' ****''

Murine coronavirus Murine coronavirus (M-CoV) is a virus in the genus ''Betacoronavirus'' that infects mice. Belonging to the subgenus ''Embecovirus'', murine coronavirus strains are enterotropic or polytropic. Enterotropic strains include mouse hepatitis virus (M ...

'' ****''

Myodes coronavirus 2JL14 ''Myodes coronavirus 2JL14'' is a species of coronavirus in the genus ''Betacoronavirus ''Betacoronavirus'' (β-CoVs or Beta-CoVs) is one of four genera (''Alpha''-, ''Beta-'', '' Gamma-'', and '' Delta-'') of coronaviruses. Member viruses ...

'' ***'' Hibecovirus'' ****'' Bat Hp-betacoronavirus Zhejiang2013'' ***''

Merbecovirus ''Merbecovirus'' is a subgenus of viruses in the genus ''Betacoronavirus'', including the human pathogen Middle East respiratory syndrome–related coronavirus (MERS-CoV). The viruses in this subgenus were previously known as group 2c coronaviru ...

'' ****''

Hedgehog coronavirus 1 ''Hedgehog coronavirus 1'' is a mammalian Group C '' Betacoronavirus'', a positive-sense RNA virus, discovered in European hedgehogs (''Erinaceus europaeus'') from Germany and first described in 2014. Most ''Betacoronavirus'' clade c viruses are ...

'' ****''

Middle East respiratory syndrome-related coronavirus ''Middle East respiratory syndrome–related coronavirus'' (''MERS-CoV''), or EMC/2012 ( HCoV-EMC/2012), is the virus that causes Middle East respiratory syndrome (MERS). It is a species of coronavirus which infects humans, bats, and camels. Th ...

'' (MERS-CoV) ****''

Pipistrellus bat coronavirus HKU5 ''Pipistrellus bat coronavirus HKU5'' (''Bat-CoV HKU5'') is an enveloped, positive-sense single-stranded RNA mammalian Group 2 '' Betacoronavirus'' discovered in Japanese ''Pipistrellus'' in Hong Kong. This strain of coronavirus is closely relat ...

'' ****''

Tylonycteris bat coronavirus HKU4 ''Tylonycteris bat coronavirus HKU4'' (''Bat-CoV HKU4'') is an enveloped, positive-sense single-stranded RNA virus mammalian Group 2 ''Betacoronavirus'' that has been found to be genetically related to the '' Middle East respiratory syndrome-rela ...

'' ***''

Nobecovirus ''Nobecovirus'' is a subgenus of viruses in the genus ''Betacoronavirus''. The viruses in the group were previously known as group 2d coronaviruses. Structure The viruses of this subgenus, like other coronaviruses, have a lipid bilayer envelope ...

'' ****''

Eidolon bat coronavirus C704 ''Eidolon bat coronavirus C704'' is a species of coronavirus in the genus ''Betacoronavirus ''Betacoronavirus'' (β-CoVs or Beta-CoVs) is one of four genera (''Alpha''-, ''Beta-'', '' Gamma-'', and '' Delta-'') of coronaviruses. Member viru ...

'' ****''

Rousettus bat coronavirus GCCDC1 ''Rousettus bat coronavirus GCCDC1'' is a species of coronavirus in the genus ''Betacoronavirus ''Betacoronavirus'' (β-CoVs or Beta-CoVs) is one of four genera (''Alpha''-, ''Beta-'', '' Gamma-'', and '' Delta-'') of coronaviruses. Member ...

'' ****''

Rousettus bat coronavirus HKU9 ''Rousettus bat coronavirus HKU9'' (''HKU9-1'') is an enveloped, positive-sense, single-stranded RNA mammalian Group 2 ''Betacoronavirus'' discovered in ''Rousettus'' bats in China in 2011. This strain of coronavirus is closely related to the EM ...

'' ***''

Sarbecovirus ''Severe acute respiratory syndrome–related coronavirus'' (SARSr-CoV or SARS-CoV)The terms ''SARSr-CoV'' and ''SARS-CoV'' are sometimes used interchangeably, especially prior to the discovery of SARS-CoV-2. This may cause confusion when some ...

'' ****''

Severe acute respiratory syndrome–related coronavirus ''Severe acute respiratory syndrome–related coronavirus'' (SARSr-CoV or SARS-CoV)The terms ''SARSr-CoV'' and ''SARS-CoV'' are sometimes used interchangeably, especially prior to the discovery of SARS-CoV-2. This may cause confusion when some ...

'' *****'' Severe acute respiratory syndrome coronavirus'' (SARS-CoV) *****'' Severe acute respiratory syndrome coronavirus 2'' (SARS-CoV-2, cause of COVID-19) **''

Gammacoronavirus ''Gammacoronavirus'' (Gamma-CoV) is one of the four genera (''Alpha''-, '' Beta-'', ''Gamma-'', and '' Delta-'') of coronaviruses. It is in the subfamily ''Orthocoronavirinae'' of the family ''Coronaviridae''. They are enveloped, positive-sens ...

'' ***'' Brangacovirus'' ****'' Goose coronavirus CB17'' ***'' Cegacovirus'' ****'' Beluga whale coronavirus SW1'' ***'' Igacovirus'' ****'' Avian coronavirus'' ****'' Avian coronavirus 9203'' ****'' Duck coronavirus 2714'' **''

Deltacoronavirus ''Deltacoronavirus'' (Delta-CoV) is one of the four genera ('' Alpha-'', '' Beta-'', '' Gamma-'', and ''Delta-'') of coronaviruses. It is in the subfamily ''Orthocoronavirinae'' of the family ''Coronaviridae''. They are enveloped, positive-se ...

'' ***'' Andecovirus'' ****'' Wigeon coronavirus HKU20'' ***'' Buldecovirus'' ****'' Bulbul coronavirus HKU11'' ****'' Common moorhen coronavirus HKU21'' ****'' Coronavirus HKU15'' ****'' Munia coronavirus HKU13'' ****'' White-eye coronavirus HKU16'' ***'' Herdecovirus'' ****'' Night heron coronavirus HKU19''

References

External links

Virus Pathogen Database and Analysis Resource (ViPR): CoronaviridaeInternational Committee on Taxonomy of Viruses
{{Authority control Nidovirales Virus families