This article is about the group of viruses.

For the disease involved in the ongoing COVID-19 pandemic, see Coronavirus disease

2019. For the virus that causes this disease, see Severe acute respiratory syndrome coronavirus  2. For the upcoming Indian film,
see Coronavirus (film).

Orthocoronavirinae

Transmission electron

micrograph of avian infectious

bronchitis virus

Illustration of the morphology of

coronaviruses; the club-

shaped viral spike peplomers (red)

create the look of a corona

surrounding the virion when seen

with an electron microscope.

Virus classification

(unranked Virus
 ):

Realm: Riboviria

Kingdom: Orthornavirae

Phylum: Pisuviricota

Class: Pisoniviricetes

Order: Nidovirales

Family: Coronaviridae

Subfamily: Orthocoronavirin

ae

Genera[1]

 Alphacoronavirus

 Betacoronavirus

 Gammacoronavirus

 Deltacoronavirus

Synonyms[2][3][4]

 Coronavirinae

Coronaviruses are a group of related RNA viruses that cause diseases in mammals and birds. In humans,

these viruses cause respiratory tract infections that can range from mild to lethal. Mild illnesses include some cases of the common
cold (which is also caused by other viruses, predominantly rhinoviruses), while more lethal varieties can cause SARS, MERS,
and COVID-19. Symptoms in other species vary: in chickens, they cause an upper respiratory tract disease, while in cows and pigs
they cause diarrhea. There are as yet no vaccines or antiviral drugs to prevent or treat human coronavirus infections.
Coronaviruses constitute the subfamily Orthocoronavirinae, in the family Coronaviridae, order Nidovirales, and realm Riboviria.[5]
[6]
 They are enveloped viruses with a positive-sense single-stranded RNA genome and a nucleocapsid of helical symmetry.
[7]
 The genome size of coronaviruses ranges from approximately 26 to 32 kilobases, one of the largest among RNA viruses.[8] They
have characteristic club-shaped spikes that project from their surface, which in electron micrographs create an image reminiscent of
the solar corona, from which their name derives.[9]

Contents

 1Etymology
 2History
 3Microbiology
o 3.1Structure
o 3.2Genome
o 3.3Replication cycle
 3.3.1Cell entry
 3.3.2Genome translation
 3.3.3Replicase-transcriptase
 3.3.4Assembly and release
o 3.4Transmission
 4Classification
 5Origin
 6Infection in humans
o 6.1Common cold
o 6.2Severe acute respiratory syndrome (SARS)
o 6.3Middle East respiratory syndrome (MERS)
o 6.4Coronavirus disease 2019 (COVID-19)
 7Infection in animals
o 7.1Farm animals
o 7.2Domestic pets
o 7.3Laboratory animals
 8Prevention and treatment
 9See also
 10References
 11Further reading

Etymology
The name "coronavirus" is derived from Latin corona, meaning "crown" or "wreath", itself a borrowing from Greek κορώνη korṓnē,
"garland, wreath".[10][11] The name was coined by June Almeida and David Tyrrell who first observed and studied human
coronaviruses.[12] The word was first used in print in 1968 by an informal group of virologists in the journal Nature to designate the
new family of viruses.[9] The name refers to the characteristic appearance of virions (the infective form of the virus) by electron
microscopy, which have a fringe of large, bulbous surface projections creating an image reminiscent of the solar corona or halo.[9]
[12]
 This morphology is created by the viral spike peplomers, which are proteins on the surface of the virus.[13]

History
History
Coronaviruses were first discovered in the 1930s when an acute respiratory infection of domesticated chickens was shown to be
caused by infectious bronchitis virus (IBV).[14] Arthur Schalk and M.C. Hawn described in 1931 a new respiratory infection of
chickens in North Dakota. The infection of new-born chicks was characterized by gasping and listlessness. The chicks' mortality rate
was 40–90%.[15] Fred Beaudette and Charles Hudson six years later successfully isolated and cultivated the infectious bronchitis
virus which caused the disease.[16] In the 1940s, two more animal coronaviruses, mouse hepatitis virus (MHV) and transmissible
gastroenteritis virus (TGEV), were isolated.[17] It was not realized at the time that these three different viruses were related. [18]
Human coronaviruses were discovered in the 1960s. [19][20] They were isolated using two different methods in the United Kingdom and
the United States.[21] E.C. Kendall, Malcom Byone, and David Tyrrell working at the Common Cold Unit of the British Medical
Research Council in 1960 isolated from a boy a novel common cold virus B814.[22][23][24] The virus was not able to be cultivated using
standard techniques which had successfully cultivated rhinoviruses, adenoviruses and other known common cold viruses. In 1965,
Tyrrell and Byone successfully cultivated the novel virus by serially passing it through organ culture of human embryonic trachea.
[25]
 The new cultivating method was introduced to the lab by Bertil Hoorn.[26] The isolated virus when intranasally inoculated into
volunteers caused a cold and was inactivated by ether which indicated it had a lipid envelope.[22][27] Around the same time, Dorothy
Hamre[28] and John Procknow at the University of Chicago isolated a novel cold virus 229E from medical students, which they grew
in kidney tissue culture. The novel virus 229E, like the virus strain B814, when inoculated into volunteers caused a cold and was
inactivated by ether.[29]
The two novel strains B814 and 229E were subsequently imaged by electron microscopy in 1967 by Scottish virologist June
Almeida at St. Thomas Hospital in London.[30][31] Almeida through electron microscopy was able to show that B814 and 229E were
morphologically related by their distinctive club-like spikes. Not only were they related with each other, but they were
morphologically related to infectious bronchitis virus (IBV).[32] A research group at the National Institute of Health the same year was
able to isolate another member of this new group of viruses using organ culture and named the virus strain OC43 (OC for organ
culture).[33] Like B814, 229E, and IBV, the novel cold virus OC43 had distinctive club-like spikes when observed with the electron
microscope.[34][35]
The IBV-like novel cold viruses were soon shown to be also morphologically related to the mouse hepatitis virus. [17] This new group
of IBV-like viruses came to be known as coronaviruses after their distinctive morphological appearance. [9] Human coronavirus
229E and human coronavirus OC43 continued to be studied in subsequent decades.[36][37] The coronavirus strain B814 was lost. It is
not known which present human coronavirus it was.[38] Other human coronaviruses have since been identified, including SARS-
CoV in 2003, HCoV NL63 in 2004, HCoV HKU1 in 2005, MERS-CoV in 2012, and SARS-CoV-2 in 2019.[39][40] There have also been
a large number of animal coronaviruses identified since the 1960s.[5]