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 common cold (which is also caused by other viruses, predominantly rhinoviruses), while more lethal varieties can cause SARS, MERS and COVID-19. In cows and pigs they cause diarrhea, while in mice they cause hepatitis and encephalomyelitis.
This article is about the group of viruses. For the disease involved in the COVID-19 pandemic, see COVID-19. For the virus that causes this disease, see SARS-CoV-2.Coronaviruses constitute the subfamily Orthocoronavirinae, in the family Coronaviridae, order Nidovirales and realm Riboviria.[3][4] They are enveloped viruses with a positive-sense single-stranded RNA genome and a nucleocapsid of helical symmetry.[5] The genome size of coronaviruses ranges from approximately 26 to 32 kilobases, one of the largest among RNA viruses.[6] They have characteristic club-shaped spikes that project from their surface, which in electron micrographs create an image reminiscent of the stellar corona, from which their name derives.[7]
Etymology
The name "coronavirus" is derived from Latin corona, meaning "crown" or "wreath", itself a borrowing from Greek κορώνη korṓnē, "garland, wreath".[8][9] The name was coined by June Almeida and David Tyrrell who first observed and studied human coronaviruses.[10] 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.[7] 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.[7][10] This morphology is created by the viral spike peplomers, which are proteins on the surface of the virus.[11]
The scientific name Coronavirus was accepted as a genus name by the International Committee for the Nomenclature of Viruses (later renamed International Committee on Taxonomy of Viruses) in 1971.[12] As the number of new species increased, the genus was split into four genera, namely Alphacoronavirus, Betacoronavirus, Deltacoronavirus, and Gammacoronavirus in 2009.[13] The common name coronavirus is used to refer to any member of the subfamily Orthocoronavirinae.[4] As of 2020, 45 species are officially recognised.[14]
Coronaviruses form the subfamily Orthocoronavirinae,[2][3][4] which is one of two subfamilies in the family Coronaviridae, order Nidovirales, and realm Riboviria.[42][70] They are divided into the four genera: Alphacoronavirus, Betacoronavirus, Gammacoronavirus and Deltacoronavirus. Alphacoronaviruses and betacoronaviruses infect mammals, while gammacoronaviruses and deltacoronaviruses primarily infect birds.[71][72]
Prevention and treatment
A number of vaccines using different methods have been developed against human coronavirus SARS-CoV-2.[146][147] Antiviral targets against human coronaviruses have also been identified such as viral proteases, polymerases, and entry proteins. Drugs are in development which target these proteins and the different steps of viral replication.[148][147]
Vaccines are available for animal coronaviruses IBV, TGEV, and Canine CoV, although their effectiveness is limited. In the case of outbreaks of highly contagious animal coronaviruses, such as PEDV, measures such as destruction of entire herds of pigs may be used to prevent transmission to other herds.[49]