''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 viruses which infect

amphibian Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arbo ...

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

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...

s. The group includes the subfamilies '' Letovirinae'' 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

coronavirus 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 co ...

es. 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 " peplomers" 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 and poly(A) tract, 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 The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough 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 i ...

, invariably contains two virus-specified

glycoprotein Glycoproteins are proteins which contain oligosaccharide chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glyco ...

species, known as the spike (S) and membrane (M) proteins. The spike protein makes up the large surface projections (sometimes known as peplomers), 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 Hemagglutinin esterase (HEs) is a glycoprotein that certain enveloped viruses possess and use as an invading mechanism. HEs helps in the attachment and destruction of certain sialic acid receptors that are found on the host cell surface. Viruses ...

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 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 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 cell infection. Once replication has been completed and the host cell is exhausted of all resources in making viral progeny, the viruses ...

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 eukaryo ...

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 ...

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'' **''

'' **'' Letovirinae'' ***''

Alphaletovirus ''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 ...

'' ****''

Milecovirus ''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 ...

'' *****'' 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 The common cold or the cold is a viral infectious disease of the upper respiratory tract that primarily affects the respiratory mucosa of the nose, throat, sinuses, and larynx. Signs and symptoms may appear fewer than two days after expos ...

, 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 t ...

, 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, which causes MERS; 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 quick ...

. 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 viruses with a positive-sense single-stranded RNA

and a

nucleocapsid 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 ...

of helical symmetry. The genome size of coronaviruses ranges from approximately 26 to 32 kilobases, among the largest for an

RNA virus An RNA virus is a virusother than a retrovirusthat has ribonucleic acid ( RNA) as its genetic material. The nucleic acid is usually single-stranded RNA (ssRNA) but it may be double-stranded (dsRNA). Notable human diseases caused by 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 ...

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'' ***'' Colacovirus'' ****'' Bat coronavirus CDPHE15'' ***'' Decacovirus'' ****''

Bat coronavirus HKU10 ''Bat coronavirus HKU10'' is a species of coronavirus in the genus ''Alphacoronavirus Alphacoronaviruses (Alpha-CoV) are members of the first of the four genera (''Alpha''-, '' Beta-'', '' Gamma-'', and '' Delta-'') of coronaviruses. They a ...

'' ****''

Rhinolophus ferrumequinum alphacoronavirus HuB-2013 ''Rhinolophus ferrumequinum alphacoronavirus HuB-2013'' is a species of coronavirus in the genus ''Alphacoronavirus Alphacoronaviruses (Alpha-CoV) are members of the first of the four genera (''Alpha''-, '' Beta-'', '' Gamma-'', and '' Delta- ...

'' ***'' Duvinacovirus'' ****'' Human coronavirus 229E'' ***'' Luchacovirus'' ****'' Lucheng Rn rat coronavirus'' ***'' Minacovirus'' ****''

Mink coronavirus 1 ''Minacovirus'' 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-se ...

'' ***'' Minunacovirus'' ****'' Miniopterus bat coronavirus 1'' ****'' Miniopterus bat coronavirus HKU8'' ***'' Myotacovirus'' ****'' Myotis ricketti alphacoronavirus Sax-2011'' ***'' Nyctacovirus'' ****''

Nyctalus velutinus alphacoronavirus SC-2013 ''Nyctalus velutinus alphacoronavirus SC-2013'' is a species of coronavirus in the genus ''Alphacoronavirus Alphacoronaviruses (Alpha-CoV) are members of the first of the four genera (''Alpha''-, '' Beta-'', '' Gamma-'', and '' Delta-'') of ...

'' ****'' Pipistrellus kuhlii coronavirus 3398'' ***'' Pedacovirus'' ****'' Porcine epidemic diarrhea virus'' ****'' Scotophilus bat coronavirus 512'' ***'' Rhinacovirus'' ****'' Rhinolophus bat coronavirus HKU2'' ***'' Setracovirus'' ****'' Human coronavirus NL63'' ****'' NL63-related bat coronavirus strain BtKYNL63-9b'' ***'' Soracovirus'' ****''

Sorex araneus coronavirus T14 ''Soracovirus'' 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 ...

'' ***'' Sunacovirus'' ****'' Suncus murinus coronavirus X74'' ***'' Tegacovirus'' ****''

Alphacoronavirus 1 ''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 Transmissible gastroenteritis virus or Transm ...

'' **'' Betacoronavirus'' ***'' Embecovirus'' ****'' Betacoronavirus 1'' *****'' Human coronavirus OC43'' ****''

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 ...

'' ****'' Human coronavirus HKU1'' ****'' Murine coronavirus'' ****''

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 viruse ...

'' ***'' Hibecovirus'' ****'' Bat Hp-betacoronavirus Zhejiang2013'' ***'' Merbecovirus'' ****'' Hedgehog coronavirus 1'' ****'' Middle East respiratory syndrome-related coronavirus'' (MERS-CoV) ****'' Pipistrellus bat coronavirus HKU5'' ****'' Tylonycteris bat coronavirus HKU4'' ***'' Nobecovirus'' ****''

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 vi ...

'' ****''

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. Membe ...

'' ****''

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 ''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 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 ...

'' (SARS-CoV) *****''

Severe acute respiratory syndrome coronavirus 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 ...

'' (SARS-CoV-2, cause of COVID-19) **'' Gammacoronavirus'' ***''

Brangacovirus ''Brangacovirus'' is a subgenus of viruses in the genus '' Gammacoronavirus'', consisting of a single species, ''Goose coronavirus CB17''. References Virus subgenera Gammacoronaviruses {{Virus-stub ...

'' ****''

Goose coronavirus CB17 ''Brangacovirus'' is a subgenus of viruses in the genus '' Gammacoronavirus'', consisting of a single species, ''Goose coronavirus CB17''. References Virus subgenera Gammacoronaviruses {{Virus-stub ...

'' ***''

Cegacovirus ''Beluga whale coronavirus SW1'' (Whale-CoV SW1) is a mammalian '' Gammacoronavirus'', an RNA virus, discovered through genome sequencing in the liver of a single deceased beluga whale and first described in 2008. This was the first description ...

'' ****''

Beluga whale coronavirus SW1 ''Beluga whale coronavirus SW1'' (Whale-CoV SW1) is a mammalian '' Gammacoronavirus'', an RNA virus, discovered through genome sequencing in the liver of a single deceased beluga whale and first described in 2008. This was the first description ...

'' ***''

Igacovirus ''Igacovirus'' is a subgenus of viruses in the genus '' Gammacoronavirus''. Species The genus consists of the following three species: * ''Avian coronavirus ''Avian coronavirus'' is a species of virus from the genus '' Gammacoronavirus'' t ...

'' ****''

Avian coronavirus ''Avian coronavirus'' is a species of virus from the genus '' Gammacoronavirus'' that infects birds; since 2018, all gammacoronaviruses which infect birds have been classified as this single species. The strain of avian coronavirus previously k ...

'' ****''

Avian coronavirus 9203 ''Avian coronavirus 9203'' is a species of coronavirus in the genus '' Gammacoronavirus''. References Gammacoronaviruses {{Virus-stub ...

'' ****''

Duck coronavirus 2714 ''Duck coronavirus 2714'' is a species of coronavirus in the genus '' Gammacoronavirus''. References Gammacoronaviruses {{Virus-stub ...

'' **'' Deltacoronavirus'' ***''

Andecovirus ''Andecovirus'' is a subgenus of viruses in the genus '' Deltacoronavirus'', consisting of a single species, ''Wigeon coronavirus HKU20''. References Virus subgenera Deltacoronaviruses {{Virus-stub ...

'' ****''

Wigeon coronavirus HKU20 ''Andecovirus'' is a subgenus of viruses in the genus '' Deltacoronavirus'', consisting of a single species, ''Wigeon coronavirus HKU20''. References Virus subgenera Deltacoronaviruses {{Virus-stub ...

'' ***''

Buldecovirus ''Buldecovirus'' is a subgenus of viruses in the genus '' Deltacoronavirus''. References {{Taxonbar, from=Q57754709 Virus subgenera Deltacoronaviruses ...

'' ****''

Bulbul coronavirus HKU11 ''Bulbul coronavirus HKU11'' (Bulbul-CoV HKU11) is a positive-sense single-stranded RNA ''Deltacoronavirus ''Deltacoronavirus'' (Delta-CoV) is one of the four genera ('' Alpha-'', '' Beta-'', '' Gamma-'', and ''Delta-'') of coronaviruses. I ...

'' ****''

Common moorhen coronavirus HKU21 ''Common moorhen coronavirus HKU21'' is a species of coronavirus in the genus '' Deltacoronavirus''. References Deltacoronaviruses {{Virus-stub ...

'' ****'' Coronavirus HKU15'' ****''

Munia coronavirus HKU13 ''Munia coronavirus HKU13'' is a species of coronavirus in the genus ''Deltacoronavirus ''Deltacoronavirus'' (Delta-CoV) is one of the four genera ('' Alpha-'', '' Beta-'', '' Gamma-'', and ''Delta-'') of coronaviruses. It is in the subfamil ...

'' ****''

White-eye coronavirus HKU16 ''White-eye coronavirus HKU16'' is a species of coronavirus in the genus '' Deltacoronavirus''. References Deltacoronaviruses {{Virus-stub ...

'' ***''

Herdecovirus ''Herdecovirus'' is a subgenus of viruses in the genus '' Deltacoronavirus'', consisting of a single species, ''Night heron coronavirus HKU19''. References Virus subgenera Deltacoronaviruses {{Virus-stub ...

'' ****''

Night heron coronavirus HKU19 ''Herdecovirus'' is a subgenus of viruses in the genus '' Deltacoronavirus'', consisting of a single species, ''Night heron coronavirus HKU19''. References Virus subgenera Deltacoronaviruses {{Virus-stub ...

References

External links

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