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| A coronavirus that may cause SARS. (transwikied from en.wikipedia. |
Coronaviruses are species in the genera of virus belonging to the subfamily Coronavirinae in the family Coronaviridae.[1][2] Coronaviruses are enveloped viruses with a positive-sense RNA genome and with a nucleocapsid of helical symmetry. The genomic size of coronaviruses ranges from approximately 26 to 32 kilobases, extraordinarily large for an RNA virus. The name "coronavirus" is derived from the Latin corona, meaning crown or halo, and refers to the characteristic appearance of virions under electron microscopy (E.M.) with a fringe of large, bulbous surface projections creating an image reminiscent of the solar corona.
This morphology is created 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 the SARS coronavirus (see below), a defined receptor-binding domain on S mediates the attachment of the virus to its cellular receptor, angiotensin-converting enzyme 2 (ACE2).[3] Some coronaviruses (specifically the members of Betacoronavirus subgroup A) also have a shorter spike-like protein called hemagglutinin esterase (HE).[1]
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-CoV which causes 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 colds 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 rhinoviruses (another common cold virus), human coronaviruses are difficult to grow in the laboratory.
In chickens, the Infectious bronchitis virus (IBV), a coronavirus, targets not only the respiratory tract but also the uro-genital tract. The virus can spread to different organs throughout the chicken.
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 coronavirus, TGE) and bovine coronavirus, which both result in diarrhea in young animals. Feline Coronavirus: two forms, 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 virologists interested in veterinary and zoonotic diseases.
Severe acute respiratory syndrome
Main article: Severe acute respiratory syndrome
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 8,000 infections, about 10% of which resulted in death.[3] 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."[5]
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.[6]
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. In September 2012, what is believed to be a new type of coronavirus, tentatively referred to as Novel Coronavirus 2012,[7] being similar to SARS (but still distinct from it, and also different from the common cold-causing coronavirus) was discovered in Qatar and Saudi Arabia.[8] The World Health Organisation has issued a global alert accordingly[9] and issued an interim case definition to help countries strengthen health protection measures against the new virus.[10] The WHO update on 28 September 2012 said that the virus did not seem to transmit easily from person to person.[11]
Some confusion exists between Novel Corona Virus 2012 (NCoV) and Human Corona Virus-Erasmus Medical Centre (HCoV-EMC). Both variants are the same. The name Novel Corona Virus 2012 (NCoV) was given to the virus before it was properly sequenced. When the Dutch Erasmus Medical Centre managed to do just that, the virus was given its proper scientific name, in line with accepted procedure.
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