# Coronaviridae

Coronaviridae is a family of enveloped, positive-strand RNA viruses which infect fish, amphibians, birds, and mammals. Commonly referred to as coronaviruses in the English language, the family coronaviridae includes the subfamilies Letovirinae and Orthocoronavirinae; the latter also known as coronavirinae.
The viral genome is 26–32 kilobases 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.

## Virology

The 5' and 3' ends of the genome have a cap and poly(A) tract, respectively. The viral envelope, obtained by budding through membranes of the endoplasmic reticulum (ER) or Golgi apparatus, invariably contains two virus-specified glycoprotein 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 is a triple-spanning transmembrane protein. Toroviruses 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 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 (E), thought to be involved in viral budding.
Genetic recombination can occur when at least two viral genomes 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. 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
** Orthocoronavirinae
** Letovirinae
*** 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 infections. 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, which causes SARS; MERS-CoV, which causes MERS; and SARS-CoV-2, which causes COVID-19. 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 genome and a nucleocapsid of helical symmetry. The genome size of coronaviruses ranges from approximately 26 to 32 kilobases, among the largest for an RNA virus (second only to a 41-kb nidovirus recently discovered in planaria).

#### Orthocoronavirinae taxonomy

* Orthocoronavirinae
** Alphacoronavirus
*** Colacovirus
**** Bat coronavirus CDPHE15
*** Decacovirus
**** Bat coronavirus HKU10
**** Rhinolophus ferrumequinum alphacoronavirus HuB-2013
*** Duvinacovirus
**** Human coronavirus 229E
*** Luchacovirus
**** 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
**** 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
*** Sunacovirus
**** Suncus murinus coronavirus X74
*** Tegacovirus
**** Alphacoronavirus 1
** Betacoronavirus
*** Embecovirus
**** Betacoronavirus 1
***** Human coronavirus OC43
**** China Rattus coronavirus HKU24
**** Human coronavirus HKU1
**** Murine coronavirus
**** Myodes coronavirus 2JL14
*** 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
**** Rousettus bat coronavirus GCCDC1
**** Rousettus bat coronavirus HKU9
*** Sarbecovirus
**** Severe acute respiratory syndrome–related coronavirus
***** Severe acute respiratory syndrome coronavirus (SARS-CoV)
***** Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, cause of COVID-19)
** Gammacoronavirus
*** Brangacovirus
**** Goose coronavirus CB17
*** Cegacovirus
**** Beluga whale coronavirus SW1
*** Igacovirus
**** Avian coronavirus
**** Avian coronavirus 9203
**** Duck coronavirus 2714
** Deltacoronavirus
*** 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