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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 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. 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][4] They are enveloped viruses with a positive-sense single-stranded RNA genome and a nucleocapsid of helical symmetry.[6] The genome size of coronaviruses ranges from approximately 26 to 32 kilobases, one of the largest among RNA viruses.[7] 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.[8]

In December 2019, a pneumonia outbreak was reported in Wuhan, China.[122] On 31 December 2019, the outbreak was traced to a novel strain of coronavirus,[123] which was given the interim name 2019-nCoV by the World Health Organization (WHO),[124][125][126] later renamed SARS-CoV-2 by the International Committee on Taxonomy of Viruses.

As of 9 November 2020, there have been at least 1,256,177[107] confirmed deaths and more than 50,395,174[107] confirmed cases in the COVID-19 pandemic. The Wuhan strain has been identified as a new strain of Betacoronavirus from group 2B with approximately 70% genetic similarity to the SARS-CoV.[127] The virus has a 96% similarity to a bat coronavirus, so it is widely suspected to originate from bats as well.[128][129] The pandemic has resulted in travel restrictions and nationwide lockdowns in many countries.

Infection in animals

Coronaviruses have been recognized as causing pathological conditions in veterinary medicine since the 1930s.[20] They infect a range of animals including swine, cattle, horses, camels, cats, dogs, rodents, birds and bats.[130] The majority of animal related coronaviruses infect the intestinal tract and are transmitted by a fecal-oral route.[131] Significant research efforts have been focused on elucidating the viral pathogenesis of

In September 2012, a new type of coronavirus was identified, initially called Novel Coronavirus 2012, and now officially named Middle East respiratory syndrome coronavirus (MERS-CoV).[112][113] The World Health Organization issued a global alert soon after.[114] The WHO update on 28 September 2012 said the virus did not seem to pass easily from person to person.[115] However, on 12 May 2013, a case of human-to-human transmission in France was confirmed by the French Ministry of Social Affairs and Health.[116] In addition, cases of human-to-human transmission were reported by the Ministry of Health in Tunisia. Two confirmed cases involved people who seemed to have caught the disease from their late father, who became ill after a visit to Qatar and Saudi Arabia. Despite this, it appears the virus had trouble spreading from human to human, as most individuals who are infected do not transmit the virus.[117] By 30 October 2013, there were 124 cases and 52 deaths in Saudi Arabia.[118]

After the Dutch Erasmus Medical Centre sequenced the virus, the virus was given a new name, Human Coronavirus—Erasmus Medical Centre (HCoV-EMC). The final name for the virus is Middle East respiratory syndrome coronavirus (MERS-CoV). The only U.S. cases (both survived) were recorded in May 2014.After the Dutch Erasmus Medical Centre sequenced the virus, the virus was given a new name, Human Coronavirus—Erasmus Medical Centre (HCoV-EMC). The final name for the virus is Middle East respiratory syndrome coronavirus (MERS-CoV). The only U.S. cases (both survived) were recorded in May 2014.[119]

In May 2015, an outbreak of MERS-CoV occurred in the Republic of Korea, when a man who had traveled to the Middle East, visited four hospitals in the Seoul area to treat his illness. This caused one of the largest outbreaks of MERS-CoV outside the Middle East.[120] As of December 2019, 2,468 cases of MERS-CoV infection had been confirmed by laboratory tests, 851 of which were fatal, a mortality rate of approximately 34.5%.[121]

In December 2019, a pneumonia outbreak was reported in Wuhan, China.[122] On 31 December 2019, the outbreak was traced to a novel strain of coronavirus,[123] which was given the interim name 2019-nCoV by the World Health Organization (WHO),[124][125][126] later renamed SARS-CoV-2 by the International Committee on Taxonomy of Viruses.

As of 9 November 2020, there have been at least 1,256,177[107] confirmed deaths and more than 50,395,174[107] confirmed cases in the As of 9 November 2020, there have been at least 1,256,177[107] confirmed deaths and more than 50,395,174[107] confirmed cases in the COVID-19 pandemic. The Wuhan strain has been identified as a new strain of Betacoronavirus from group 2B with approximately 70% genetic similarity to the SARS-CoV.[127] The virus has a 96% similarity to a bat coronavirus, so it is widely suspected to originate from bats as well.[128][129] The pandemic has resulted in travel restrictions and nationwide lockdowns in many countries.

Coronaviruses have been recognized as causing pathological conditions in veterinary medicine since the 1930s.[20] They infect a range of animals including swine, cattle, horses, camels, cats, dogs, rodents, birds and bats.[130] The majority of animal related coronaviruses infect the intestinal tract and are transmitted by a fecal-oral route.[131] Significant research efforts have been focused on elucidating the viral pathogenesis of these animal coronaviruses, especially by virologists interested in veterinary and zoonotic diseases.[132]

Farm animals

Coronaviruses

Coronaviruses infect domesticated birds.[133] Infectious bronchitis virus (IBV), a type of coronavirus, causes avian infectious bronchitis.[134] The virus is of concern to the poultry industry because of the high mortality from infection, its rapid spread, and its effect on production.[130] The virus affects both meat production and egg production and causes substantial economic loss.[135] In chickens, infectious bronchitis virus targets not only the respiratory tract but also the urogenital tract. The virus can spread to different organs throughout the chicken.[134] The virus is transmitted by aerosol and food contaminated by feces. Different vaccines against IBV exist and have helped to limit the spread of the virus and its variants.[130] Infectious bronchitis virus is one of a number of strains of the species Avian coronavirus.[136] Another strain of avian coronavirus is turkey coronavirus (TCV) which causes enteritis in turkeys.[130]

Coronaviruses also affect other branches of animal husbandry such as pig farming and the cattle raising.[130] Swine acute diarrhea syndrome coronavirus (SADS-CoV), which is related to bat coronavirus HKU2, causes diarrhea in pigs.[137] Porcine epidemic diarrhea virus (PEDV) is a coronavirus that has recently emerged and similarly causes diarrhea in pigs.[138] Transmissible gastroenteritis virus (TGEV), which is a member of the species Alphacoronavirus 1,[139] is another coronavirus that causes diarrhea in young pigs.[140][141] In the cattle industry bovine coronavirus (BCV), which is a member of the species Betacoronavirus 1 and related to HCoV-OC43,[142] is responsible for severe profuse enteritis in young calves.[130]

Coronaviruses infect domestic pets such as cats, dogs, and ferrets.[133] There are two forms of feline coronavirus which are both members of the species Alphacoronavirus 1.[139] 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 with high mortality.[130] There are two different coronaviruses that infect dogs. Canine coronavirus (CCoV), which is a member of the species Alphacoronavirus 1,[139] causes mild gastrointestinal disease.[130] Canine respiratory coronavirus (CRCoV), which is a member of the species Betacoronavirus 1 and related to HCoV-OC43,[142] cause respiratory disease.[130] Similarly, there are two types of coronavirus that infect ferrets.[143] Ferret enteric coronavirus causes a gastrointestinal syndrome known as epizootic catarrhal enteritis (ECE), and a more lethal systemic version of the virus (like FIP in cats) known as ferret systemic coronavirus (FSC).[144][145]

Laboratory animalsCoronaviruses infect laboratory animals.[130] Mouse hepatitis virus (MHV), which is a member of the species Murine coronavirus,[146] causes an epidemic murine illness with high mortality, especially among colonies of laboratory mice.[147] Prior to the discovery of SARS-CoV, MHV was 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.[132] Sialodacryoadenitis virus (SDAV), which is a strain of the species Murine coronavirus,[146] is highly infectious coronavirus of laboratory rats, which can be transmitted between individuals by direct contact and indirectly by aerosol. Rabbit enteric coronavirus causes acute gastrointestinal disease and diarrhea in young European rabbits.[130] Mortality rates are high.[148]

Prevention and treatment<

There are no vaccines or antiviral drugs to prevent or treat human coronavirus infections. Treatment is only supportive. A number of antiviral targets have 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. A number of vaccines using different methods are also under development for different human coronaviruses.[50]

There are no antiviral drugs to treat animal coronaviruses.[citation needed] Vaccines are available for 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.[50]