Коронавирустар: Тұқымдастығы, түрлері және аурулары

Subfamily of viruses in the family Coronaviridae

the group of viruses

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. Coronaviruses constitute the subfamily Orthocoronavirinae, in the family Coronaviridae, order Nidovirales and realm Riboviria. The genome size of coronaviruses ranges from approximately 26 to 32 kilobases, one of the largest among RNA viruses. 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.

The name "coronavirus" is derived from Latin corona, meaning "crown" or "wreath", itself a borrowing from Greek κορώνη korṓnē, "garland, wreath". The name was coined by June Almeida and David Tyrrell who first observed and studied human coronaviruses. This morphology is created by the viral spike peplomers, which are proteins on the surface of the virus. 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. As the number of new species increased, the genus was split into four genera, namely Alphacoronavirus, Betacoronavirus, Deltacoronavirus, and Gammacoronavirus in 2009. The common name coronavirus is used to refer to any member of the subfamily Orthocoronavirinae. As of 2020, 45 species are officially recognised.

Although the common cold is usually caused by rhinoviruses, in about 15% of cases the cause is a coronavirus. The human coronaviruses HCoV OC43, HCoV HKU1, HCoV 229E, and HCoV NL63 continually circulate in the human population in adults and children worldwide and produce the generally mild symptoms of the common cold. The four mild coronaviruses have a seasonal incidence occurring in the winter months in temperate climates. There is no preponderance in any season in tropical climates.

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 (WHO) issued a press release stating that a novel coronavirus identified by several laboratories was the causative agent for SARS. The virus was officially named the SARS coronavirus (SARS CoV). More than 8,000 people from 29 countries and territories were infected, and at least 774 died. The World Health Organization issued a global alert soon after. The WHO update on 28 September 2012 said the virus did not seem to pass easily from person to person. 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. 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. By 30 October 2013, there were 124 cases and 52 deaths in Saudi Arabia. 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. 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. 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%.

In December 2019, a pneumonia outbreak was reported in Wuhan, China. On 31 December 2019, the outbreak was traced to a novel strain of coronavirus, which was given the interim name 2019 nCoV by the World Health Organization, later renamed SARS CoV 2 by the International Committee on Taxonomy of Viruses. As of , there were at least confirmed deaths and more than 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. The virus has a 96% similarity to a bat coronavirus, so it is widely suspected to originate from bats as well.

During a surveillance study of archived samples of Malaysian viral pneumonia patients, virologists identified a strain of canine coronavirus which has infected humans in 2018.

Coronaviruses have been recognized as causing pathological conditions in veterinary medicine since the 1930s. The majority of animal related coronaviruses infect the intestinal tract and are transmitted by a fecal oral route. Significant research efforts have been focused on elucidating the viral pathogenesis of these animal coronaviruses, especially by virologists interested in veterinary and zoonotic diseases.

Coronaviruses infect domesticated birds. Infectious bronchitis virus (IBV), a type of coronavirus, causes avian infectious bronchitis. 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. 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. Another strain of avian coronavirus is turkey coronavirus (TCV) which causes enteritis in turkeys. Porcine epidemic diarrhea virus (PEDV) is a coronavirus that has recently emerged and similarly causes diarrhea in pigs. Transmissible gastroenteritis virus (TGEV), which is a member of the species Alphacoronavirus 1, is another coronavirus that causes diarrhea in young pigs. In the cattle industry bovine coronavirus (BCV), which is a member of the species Betacoronavirus 1 and related to HCoV OC43, is responsible for severe profuse enteritis in young calves. 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).

Coronaviruses infect laboratory animals. causes an epidemic murine illness with high mortality, especially among colonies of laboratory mice. 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.

A number of vaccines using different methods have been developed against human coronavirus SARS CoV 2. 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. 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.