View source for Coronavirus

__NOTOC__
{{Taxobox
| image= corona1.jpg
| color=violet
| name = ''Coronavirus''
| virus_group = iv
| ordo = ''[[Nidovirales]]''
| familia = ''[[Coronaviridae]]''
| genus = '''''Coronavirus'''''
}}

{{SI}}
{{CMG}}

==Overview==
Coronavirus is a genus of animal [[virus]] belonging to the family ''[[Coronaviridae]]''.<ref name=Thiel>{{cite book | author = Thiel V (editor). | title = Coronaviruses: Molecular and Cellular Biology | edition = 1st ed. | publisher = Caister Academic Press | year = 2007 |  id =  ISBN 978-1-904455-16-5 }}</ref>

==Historical Perspective==
Coronaviruses were first isolated from chickens in 1937. In 1965, Tyrrell and Bynoe used cultures of human ciliated embryonal trachea to propagate the first human coronavirus (HCoV) in vitro. There are now approximately 15 species in this family, which infect not only man but cattle, pigs, rodents, cats, dogs and birds (some are serious veterinary pathogens, especially chickens).<ref name="urlCoronavirus - MicrobeWiki">{{cite web |url=http://microbewiki.kenyon.edu/index.php/Coronavirus |title=Coronavirus - MicrobeWiki |format= |work= |accessdate=2012-12-28}}</ref>

==Structure==
Coronaviruses are [[enveloped virus]]es with a positive-sense single-stranded [[RNA]] [[genome]] and a helical symmetry. The genomic size of coronaviruses ranges from approximately 16 to 31 kilobases, extraordinarily large for an RNA virus. The name coronavirus is derived from the greek (''κορώνα'', meaning crown) as the virus envelope appears under [[electron microscopy]] (E.M.) to be crowned by a characteristic ring of small bulbous structures. This [[Morphology (biology)|morphology]] is actually formed by the viral spike (S) peplomers, which are proteins that populate the surface of the virus and determine [[host tropism]]. Coronaviruses are grouped in the order [[Nidovirales]], named for the Latin (''nidus'', meaning nest) as all viruses in this order produce a 3' co-terminal nested set of subgenomic mRNA's during infection.

Proteins that contribute to the overall structure of all coronaviruses are the spike (S), envelope (E), membrane (M) and [[nucleocapsid]] (N). In the specific case of SARS , a defined receptor-binding domain on S mediates the attachment of the virus to its cellular receptor, [[angiotensin-converting enzyme 2]] (ACE2).<ref name="li">{{cite journal | author=Li, Fang, et. al. | title=Structure of SARS Coronavirus Spike Receptor-Binding Domain Complexed with Receptor | journal=Science | year=2005 | volume=309 | pages=1864&ndash;1868 | url=http://www.sciencemag.org/cgi/content/full/309/5742/1864  | doi=10.1126/science.1116480}} </ref> Members of the group 2 coronaviruses also have a shorter spike-like protein called [[hemagglutinin esterase]] (HE) encoded in their genome, but for some reason this protein is not always brought to expression (produced) in the cell.<ref>{{cite journal | author= de Haan CAM, Rottier PJM | title= Molecular Interactions in the Assembly of Coronaviruses | journal=Advances in Virus Research | year=2005 | volume=64 | pages=185&ndash;186 }}</ref>
==Classification==
===Based on Groups===
*Genus '''''Coronavirus'''''
**Group 1
***''[[Canine coronavirus]]'' (CCoV) 
***''Feline coronavirus'' (FeCoV) 
***''Human coronavirus 229E (HCoV-229E) 
***''Porcine epidemic diarrhea virus (PEDV) 
***''Transmissible gastroenteritis virus'' (TGEV)
***''Human Coronavirus NL63'' (NL or New Haven)
***''Human Coronavirus 229E''
**Group 2
***''Bovine coronavirus'' (BCoV) 
***''[[Canine coronavirus|Canine respiratory coronavirus]]'' (CRCoV) - Common in SE Asia and Micronesia
***''Human coronavirus OC43'' (HCoV-OC43) 
***''[[Mouse hepatitis virus]]'' (MHV) 
***''Porcine hemagglutinating encephalomyelitis virus'' (HEV) 
***''Rat coronavirus'' (RCV) Rat Coronavirus is quite prevalent in Eastern Australia where, as of March/April 2008, it has been found among native and feral rodents colonies. 
***''Turkey coronavirus'' (TCoV) 
***''(No common name as of yet)'' (HCoV-HKU1)<ref>{{cite journal | author=Woo PC, Lau SK, Chu CM, ''et al.'' | title=Characterization and complete genome sequence of a novel coronavirus, coronavirus HKU1, from patients with pneumonia | journal=J Virol | year=2005 | volume=79 | pages=884&ndash;95  | doi=10.1128/JVI.79.2.884-895.2005}}</ref><ref>{{cite journal | author=Vabret A, Dina J, Gouarin S, ''et al.'' | title=Detection of the new human coronavirus HKU1: a report of 6 cases | journal=Clin Infect Dis | year=2006 | volume=42 | pages=634&ndash;9  | doi=10.1086/500136}}</ref> 
**Group 3
***''[[avian infectious bronchitis virus|Infectious bronchitis virus]]'' (IBV)
***''[[Turkey coronavirus]]'' (Bluecomb disease virus)
***''Goose coronavirus''
***''Duck coronavirus''

===Based on Baltimore Classification===
The Baltimore classification, developed by David Baltimore, is a virus classification system that groups viruses into families, depending on their type of genome (DNA, RNA, single-stranded (ss), double-stranded (ds), etc.) and their method of replication.<ref name="urlCoronavirus - MicrobeWiki">{{cite web |url=http://microbewiki.kenyon.edu/index.php/Coronavirus |title=Coronavirus - MicrobeWiki |format= |work= |accessdate=2012-12-28}}</ref>
* Virus
* ssRNA positive-strand viruses
* no DNA stage
* Nidovirales
* Coronaviridae
* ''Coronavirus''

===Human Coronaviruses===

*HCoV-229E
*HCoV-OC43
*SARS-CoV
*NL63/NL/New Haven coronavirus
*HKU1-CoV
*Novel Coronavirus 2012
*HCoV-EMC

== Replication of Coronaviruses ==
[[Image:coronavirus_replication.png|thumb|center|500px|The infection cycle of coronavirus]]
<br clear="left"/>
Replication of Coronavirus begins with entry to the cell takes place in the [[cytoplasm]] in a membrane-protected microenvironment, upon entry to the cell the virus particle is uncoated and the RNA genome is deposited into the cytoplasm. The Coronavirus genome has a 5’ methylated cap and a 3’polyadenylated-A tail to make it look as much like the host RNA as possible. This also allows the RNA to attach to ribosomes for translation. Coronaviruses also have a protein known as a replicase encoded in its genome which allows the RNA viral genome to be translated into RNA through using the host cells machinery. The replicase is the first protein to be made as once the gene encoding the replicase is translated the translation is stopped by a stop codon. This is known as a nested transcript, where the transcript only encodes one gene- it is monocistronic. The RNA genome is replicated and a long polyprotein is formed, where all of the proteins are attached. Coronaviruses have a non-structural protein called a protease which is able to separate the proteins in the chain. This is a form of genetic economy for the virus allowing it to encode the most amounts of genes in a small amount of nucleotides.

Coronavirus transcription involves a discontinuous [[RNA]] synthesis (template switch) during the extension of a negative copy of the subgenomic mRNAs. Basepairing during transcription is a requirement. Coronavirus N protein is required for coronavirus [[RNA]] synthesis, and has RNA chaperone activity that may be involved in template switch. Both viral and cellular proteins are required for replication and transcription. Coronaviruses initiate translation by cap-dependent and cap-independent mechanisms. Cell macromolecular synthesis may be controlled after Coronavirus infection by locating some virus proteins in the host cell nucleus. Infection by different coronaviruses cause in the host alteration in the transcription and translation patterns, in the cell cycle, the [[cytoskeleton]], [[apoptosis]] and [[coagulation]] pathways, [[inflammation]], and immune and stress responses.<ref name=sobrino4>{{cite book |author=Enjuanes et al|year=2008|chapter=Coronavirus Replication and Interaction with Host|title=Animal Viruses: Molecular Biology|publisher=Caister Academic Press|id= ISBN 978-1-904455-22-6}}</ref>

== Pathophysiology ==

Coronavirus infection is very common and occurs worldwide. The incidence of infection is strongly seasonal, with the greatest incidence in children in winter. Adult infections are less common. The number of coronavirus serotypes and the extent of antigenic variation is unknown. Re-infections appear to occur throughout life, implying multiple serotypes (at least four are known) and/or antigenic variation, hence the prospects for immunization appear bleak.

Coronaviruses primarily infect the upper respiratory and [[gastrointestinal tract]] of mammals and birds. Four to five different currently known strains of coronaviruses infect humans. The most publicized human coronavirus, [[SARS coronavirus|SARS-CoV]] which causes [[Severe acute respiratory syndrome|SARS]], has a unique pathogenesis because it causes both upper and lower respiratory tract infections and can also cause [[gastroenteritis]]. Coronaviruses are believed to cause a significant percentage of all [[common cold]]s in human adults. Coronaviruses cause colds in humans primarily in the winter and early spring seasons. The significance and economic impact of coronaviruses as causative agents of the common cold are hard to assess because, unlike [[rhinovirus]]es (another common cold virus), human coronaviruses are difficult to grow in the laboratory.

These viruses infect a variety of mammals & birds. The exact number of human isolates are not known as many cannot be grown in culture. In humans, they cause:

* Respiratory infections (common), including Severe Acute Respiratory Syndrome (SARS)
* Enteric infections (occasional - mostly in infants <12 months)
* Neurological syndromes (rare)

Coronaviruses also cause a range of diseases in farm animals and domesticated pets, some of which can be serious and are a threat to the farming industry. Economically significant coronaviruses of farm animals include [[porcine]] coronavirus (transmissible gastroenteritis, TGE) and [[bovine]] coronavirus, which both result in [[diarrhea]] in young animals. Feline enteric coronavirus is a pathogen of minor clinical significance, but spontaneous mutation of this virus can result in feline infectious [[peritonitis]] (FIP), a disease associated with high mortality. There are two types of [[canine coronavirus]] (CCoV), one that causes mild gastrointestinal disease and one that has been found to cause respiratory disease.  [[Mouse hepatitis virus]] (MHV) is a coronavirus that causes an epidemic [[murine]] illness with high mortality, especially among colonies of laboratory mice. Prior to the discovery of SARS-CoV, MHV had been the best-studied coronavirus both ''in vivo'' and ''in vitro'' as well as at the molecular level. Some strains of MHV cause a progressive demyelinating encephalitis in mice which has been used as a murine model for [[multiple sclerosis]]. Significant research efforts have been focused on elucidating the [[viral pathogenesis]] of these animal coronaviruses, especially by [[virologist]]s interested in veterinary and [[zoonotic]] diseases.

HCoV-229E and HCoV-OC43 cause the common cold, a self-limiting upper respiratory tract infection. Infection can lead to a number of illnesses such as bronchitis, gastroenteritis, progressive demyelinating encephalitis, diarrhea, peritonitis, nasal obstruction, rhinorrhea, sneezing, sore throat and cough. They can cause more severe lower respiratory tract infection, including pneumonia in infants, elderly and immunocompromised individuals.

HCoV-229E is a common agent if coryza, whereas HCoV-OC43 is generally characterized by sore throats.

HCoV-NL63 causes laryngotracheitis (croup) and nonfatal upper and lower respiratory tract infections in children, elderly, and immunocompromised individuals. HCoV-HKU1 causes mild upper respiratory diseases, the common cold, bronchiolitis, and pneumonia, with symptoms such as rhinorrhoea, fever, cough, febrile seizure, and wheezing. More severe illness may occur in children, adults with underlying disease, the elderly, and may be associated with gastrointestinal illness

=== Transmission ===

They are transmitted by aerosols of respiratory secretions, by the faecal-oral route, and by mechanical transmission. Most virus growth occurs in epithelial cells. Occasionally the liver, kidneys, heart or eyes may be infected, as well as other cell types such as macrophages. In cold-type respiratory infections, growth appears to be localized to the epithelium of the upper respiratory tract, but there is no adequate animal model for the human respiratory coronaviruses.

* Incubation period: 2 - 4 days.
* Communicability: Human-to-human transmission is    possible during the presence infectious droplets, which can cause infection via    inhalation, or through contaminated surfaces.

=== Role of Spike Proteins ===

* They induce neutralizing antibody.
* They are important in relating host cell tropism.
* Haemaglutination.
* They mediate the cell to cell or cell to viral fusion by the interaction between viral envelope and the specific receptor of host [[cell membrane]].

=== Severe acute respiratory syndrome ===

[[Image:Sars-corona.png|thumb|200px|left|SARS-CoV Particles]]

<br clear="left"/>
In [[2003]], following the outbreak of [[Severe acute respiratory syndrome]] (SARS) which had begun the prior year in Asia, and secondary cases elsewhere in the world, the [[World Health Organization]] issued a press release stating that a novel coronavirus identified by a number of laboratories was the causative agent for SARS. The virus was officially named the [[SARS coronavirus]] (SARS-CoV). The SARS epidemic resulted in over 8000 infections, about 10% of which resulted in death.<ref name="li" />  [[X-ray crystallography]] studies performed at the [[Advanced Light Source]] of [[Lawrence Berkeley National Laboratory]] have begun to give hope of a [[vaccine]] against the disease "since [the spike protein] appears to be recognized by the immune system of the host."<ref>{{cite web | title=Learning How SARS Spikes Its Quarry | publisher=Chevy Chase, MD: Howard Hughes Medical Institute | work=Press Release PR-HHMI-05-4 | url=http://www.lightsources.org/cms/?pid=1000828 | accessmonthday=September 16 | accessyear=2005 }} </ref>

For more information on SARS click [[Severe acute respiratory syndrome|here]].

==Epidemiology and Demographics==
Coronaviruses have a worldwide distribution, causing 10-15% of common cold cases. Infections show a seasonal pattern with most cases occurring in the winter months

==Natural History, Complications and Prognosis==
Clinically, most infections cause a mild, self-limited disease (cold or stomach upset), but there may be rare neurological complications. SARS is a form of viral pneumonia where infection encompasses the lower respiratory tract.

==Recent discoveries of novel human coronaviruses==
Following the high-profile publicity of SARS outbreaks, there has been a renewed interest in coronaviruses in the field of [[virology]]. For many years, scientists knew only about the existence of two human coronaviruses (HCoV-229E and HCoV-OC43). The discovery of SARS-CoV added another human coronavirus to the list. By the end of 2004, three independent research labs reported the discovery of a fourth human coronavirus. It has been named NL63, NL or the New Haven coronavirus by the different research groups.<ref>{{cite journal | author=van der Hoek L, Pyrc K, Jebbink MF, ''et al.'' | title=Identification of a new human coronavirus | doi= 10.1038/nm1024 | journal=Nat Med | year=2004 | volume=10 | issue=4 | pages=368&ndash;73 }}</ref> The naming of this fourth coronavirus is still a controversial issue, because the three labs are still battling over who actually discovered the virus first and hence earns the right to name the virus. Early in 2005, a research team at the University of Hong Kong reported finding a fifth human coronavirus in two [[pneumonia]] patients, and subsequently named it [[HKU1]].

==References==
{{reflist|2}}

{{Common Cold}}

[[Category:Nidovirales]]
[[Category:Animal virology]]

[[da:Coronavirus]]
[[de:Coronaviren]]
[[es:Coronavirus]]
[[fr:Coronavirus]]
[[it:Coronavirus]]
[[nl:Coronavirussen]]
[[ja:コロナウイルス]]
[[pl:Koronawirusy]]
[[pt:Coronavirus]]
[[zh:冠状病毒]]

{{WH}}
{{WS}}