Background of coronavirus in china. Coronaviruses belong to the order Nidovirales, Coronaviridae, and Coronavirus. They are important pathogens for many livestock and pets, including human diseases, and cause a variety of acute and chronic diseases. The Ninth International Committee on Classification of Virology divided the Coronaviridae into three genera, namely, alpha, beta, and gamma. Coronavirus alpha includes Coronavirus alpha1, human coronavirus 229E, human coronavirus NL63, long-winged bat coronavirus HPU1, long-winged bat coronavirus HPU8, chrysanthemum bat coronavirus HPU2, and porcine epidemic diarrhea virus (Porcineepidemicdiarrheavirus, PEDV) and other 8 species. Porcine infectious gastroenteritis virus (Transmissible gastroenteritis virus (TGEV), canine corona virus (CCoV) and feline corona virus (FCoV) are members of alpha coronavirus 1).
Coronavirus β includes 7 species including βcoronavirus 1, human coronavirus HKU1, murine coronavirus, domestic bat coronavirus HPU5, fruit bat coronavirus HPU9, and severe acute respiratory syndrome (severeacuterespiratorysyndromes, SARS). Beta coronavirus 1 includes bovine coronavirus (BCoV), human coronavirus OC43, equine coronavirus (ECoV), porcine hemagglutinating encephalomyelitis virus (PEV), and canine respiratory coronavirus (Caninerespiratorycoronavirus, CrCoV), etc .; mouse coronaviruses include Mouse Hepatitis virus (MHV), rat coronavirus and bird puffin virus; severe acute respiratory syndrome (SARS) -related viruses include SARS virus and other similar SARS viruses.
The gamma genus coronavirus includes two species of avian coronavirus and beluga coronavirus SW1. Avian coronaviruses include coronaviruses that cause infections in a variety of birds such as chickens, turkeys, sparrows, ducks, geese, and pigeons, the most important of which is the avian infectious bronchitis virus (IBV). In 2011, the Virus Classification Committee published on the Internet. According to the genetic evolution analysis of the coronavirus gene, a new genera of the Coronaviridae family—δ genera [3] , including Nightingale Coronavirus HPU11, Thrush Coronavirus HPU12, and Munia Coronavirus HPU13. . Although the first coronavirus was discovered in the 1930s, the true attention of the coronavirus was caused by the SARS epidemic caused by the SARS coronavirus (SARS-CoV) from 2002 to 2003, which spread to many countries and regions. After the social panic. Prior to this, research on coronaviruses was mostly restricted to the veterinary field. Chicken infectious bronchitis caused by IBV of the genus Genus is highly infectious in flocks and is one of the important respiratory diseases, which is very harmful to the poultry breeding industry.
Epidemiology
Coronavirus infections are distributed in many regions of the world. China and the United Kingdom, the United States, Germany, Japan, Russia, Finland, India and other countries have found the presence of the virus. The infection caused by the virus occurs mainly in winter and early spring. In a home test in Michigan, USA , it was proved that coronavirus can infect all age groups, 29.2% of them are 0 to 4 years old, and 22% are over 40 years old. This is not the same as the epidemic situation of other upper respiratory viruses, such as respiratory syncytial virus , which mostly decrease in incidence with age. In addition, rhinoviruses are not common when the coronavirus is circulating. [5]
So far, about 15 different coronavirus strains have been found that can infect a variety of mammals and birds, and some can cause disease in humans.
Human diseases caused by coronavirus are mainly respiratory infections (including severe acute respiratory syndrome , SARS). The virus is sensitive to temperature and grows well at 33 ° C, but it is suppressed at 35 ° C. Because of this characteristic, winter and early spring are the epidemic seasons of the virus disease. Coronavirus is one of the main pathogens of the common cold in adults. The infection rate in children is high, mainly upper respiratory tract infection, and it rarely spreads to the lower respiratory tract. In addition, it can cause acute gastroenteritis in infants and newborns . The main symptoms are watery stools, fever, and vomiting. It can be pulled more than 10 times a day. In severe cases, bloody stools may occur. In rare cases, it also causes nervous system syndrome. . [5]
Coronavirus is also an important cause of acute exacerbation of chronic bronchitis in adults. Studies have shown that the coronavirus that caused atypical pneumonia in many countries and regions around the world this time is not the two types known. As the outside world speculates, it is a new virus that has not been exposed to humans. Some experts previously believed that it was a "paramyxovirus group" or "interstitial pneumonia virus", but it was eventually overturned due to insufficient evidence. [5]
The growth of the virus is mostly in epithelial cells. It can also infect the liver, kidneys, heart, and eyes. It can also grow in other cell types (such as macrophages ). The human coronavirus does not yet have a suitable animal model for research (animal model of human disease refers to animals with simulated performance of human diseases established in various medical scientific research. Animal disease models are mainly used in experimental physiology, experimental pathology and experimental therapeutics (including for drug screening) study), so the coronavirus infection of the nasal mucosa , the organ culture can be separated. It is also difficult to use the above materials for the propagation of viruses. [5]
Coronavirus serotypes and antigenic variability are unknown. Coronaviruses can have repeated infections, suggesting that they have multiple serotypes (at least four are known) and have antigenic variations. Their immunity is difficult, and there are no specific preventive and therapeutic drugs.
way for spreading of coronavirus
Coronavirus is excreted through respiratory secretions , transmitted through oral fluid, sneeze , and contact, and transmitted through air droplets . The infection peaks in autumn, winter, and early spring. The virus is sensitive to heat. Ultraviolet rays, Lysol water, 0.1% peroxyacetic acid, and 1% keliaolin can kill the virus in a short time.
Precaution
There is specific prevention for its prevention, that is, targeted preventive measures ( the development of vaccines and vaccines is possible, but it takes a long time to solve the problem of virus reproduction is a problem) and non-specific preventive measures (that is, prevention of spring respiratory diseases) Measures such as keeping warm, washing hands, ventilating, avoiding excessive fatigue and contact with patients, and going to public places with fewer people, etc.).
Morphology
Coronavirus particles are irregular in shape and have a diameter of about 60-220nm. Viral particles envelope a fatty membrane, and there are three types of glycoproteins on the surface of the membrane: Spike protein (S, Spike Protein, which is a receptor binding site, cytolysis, and major antigenic site); small envelope glycoprotein (E, Envelope Protein, smaller, envelope-bound protein); membrane glycoprotein (M, Membrane Protein, responsible for transmembrane transport of nutrients, budding and release of new viruses, and formation of viral envelopes). A few species also include hemagglutinin -esterase (HE protein, Haemaglutinin-esterase). Coronavirus's nucleic acid is non-segment single-stranded (+) RNA with a length of 27-31kb. It is the longest RNA nucleic acid strand in RNA viruses . Hat ", with a PolyA" tail "structure at the 3 'end. This structure is very similar to eukaryotic mRNA, and is also an important structural basis for its genomic RNA itself to play the role of a translation template, eliminating the RNA-DNA-RNA transcription process. Coronavirus has a very high recombination rate between RNA and RNA, and the virus mutates due to this high recombination rate. After recombination, the RNA sequence has changed, and the amino acid sequence encoded by the nucleic acid has also changed. The protein composed of amino acids has changed accordingly, which has caused its antigenicity to change. As a result of changes in antigenicity, the original vaccine failed and immunity failed.
Coronavirus mature particles, there is no RNA virus replication required RNA polymerase (Viral RNA polymerase), it enters a host cell , the directly viral genomic RNA template is translated, expressed viral RNA polymerase. This enzyme is then used to complete the transcription and synthesis of the negative-strand sub-genomic RNA, the synthesis of various structural protein mRNAs, and the replication of viral genomic RNA. Coronavirus mature structural protein synthesis of mRNA, there is no post-transcriptional modification and shearing process, but directly through RNA polymerase and some transcription factors , with a "discontinuous transcription" mechanism, by identifying specific, TRS Selectively transcribe from the negative-sense RNA one-time all the components that make up a mature mRNA. After the replication of structural proteins and genomic RNA is completed, new coronavirus particles will be assembled at the endoplasmic reticulum of the host cell and secreted outside the cell through the Golgi apparatus to complete its life cycle.
Clinical features of coronavirus
Coronavirus is one of the main pathogens of the common cold in adults. It can cause upper respiratory tract infections in children , and rarely affects the lower respiratory tract . The incubation period for coronavirus infection is usually 2 to 5 days, with an average of 3 days. Typical coronavirus infections have cold symptoms such as runny nose and discomfort. Different types of viruses have different pathogenicity and cause different clinical manifestations. The symptoms caused by OC43 strain are generally more severe than those of 229E virus. Coronavirus infection can cause fever, chills , and vomiting. The course of disease is usually about 1 week, the clinical course is mild, and there are no sequelae.
Coronavirus can also cause acute gastroenteritis in infants and newborns . The main symptoms are watery stools, fever, and vomiting. More than 10 times a day, bloody stools can occur in severe cases.
Coronavirus infections have been reported in the literature to produce the following clinical symptoms:
(1) Respiratory infections, including severe acute respiratory syndrome (SARS);
(2) Intestinal infections (occasional infants);
(3) Neurological symptoms (rarely).
Coronavirus is excreted through respiratory secretions, and is transmitted through oral fluid, air injection, and contact. Clinically, most coronaviruses cause mild and self-healing diseases, but a few may have neurological complications.
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