Behind the Scenes of New Coronavirus Pneumonia-2019-nCov

Diagnostics

What is Novel Coronavirus?

Novel Coronavirus (2019-nCoV) that was first detected in Wuhan City, Hubei Province, China and which continues to expand. Chinese health officials have reported thousands of infections with 2019-nCoV in China, with the virus reportedly spreading from person-to-person in many parts of that country. Infections with 2019-nCoV, most of them associated with travel from Wuhan, also are being reported in a growing number of international locations, including the United States.

So what are the black hands behind the new pneumonia? Studies have found that mysterious pneumonia is caused by a coronavirus. Coronavirus is a member of the family Coronaviridae. It was first isolated from chickens in 1937. The diameter of the virus particles is 60-200nm, and the average diameter is 100nm. The virus has an envelope, and there are spinous processes on the envelope. The entire virus looks like a corona, and the spinous processes of different coronaviruses are significantly different.

Figure 1. Model of a novel coronavirus.

Coronavirus Structural Features

Clinical studies have found that there are three glycoproteins on the surface of the envelope membrane outside the coronavirus particle: spike glycoprotein (S, which is the receptor binding site, cytolysis and major antigenic site); small envelope glycoprotein ( E, smaller, envelope-bound protein); membrane glycoprotein (M, responsible for transmembrane transport of nutrients, budding and release of new viruses, and formation of virus envelopes). A few species also have hemagglutinin glycoprotein (HE protein). Coronavirus’s nucleic acid is non-segment single-stranded (+) RNA with a length of 27-31kd. It is the longest RNA nucleic acid strand in RNA viruses,and has important structural features unique to positive-strand RNA: that is, a methylated “cap” on the 5 ‘end of the RNA strand and a PolyA “tail” structure on 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. So the coronavirus mature particle does not contain the RNA polymerase required for RNA virus replication. After entering the host cell, it directly uses the viral genomic RNA as a translation template to express the viral RNA polymerase. This enzyme is then used to complete the synthesis of negative-strand subgenomic RNA, various structural protein mRNAs, and the replication of viral genomic RNA. In addition, because the recombination rate between the RNA of the coronavirus and the RNA is very high, the virus mutates due to this high recombination rate. After recombination, the RNA sequence changes, and the amino acid sequence encoded by the nucleic acid changes accordingly, which changes its antigenicity. As a result of changes in antigenicity, the original vaccine failed and immunity failed. This has caused greater difficulties in preventing this virus, and has also caused greater harm to humans.

What Are the Symptoms of This Coronavirus?

Symptoms include cough, which may be accompanied by fever and shortness of breath. There are early reports of non-respiratory symptoms, such as nausea, vomiting, or diarrhea. Many people recovered within a few days. However, some people, especially young people, elderly people, or people with weakened immune systems, may develop more serious infections, such as bronchitis or pneumonia.

The Difference Between 2019-nCov And Sars-Cov And Mers-Cov

Coronaviruses have caused many outbreaks in recent years, such as severe acute respiratory syndrome (SARS), the Middle East respiratory syndrome (MERS), and  novel coronavirus pneumonia. According to available clinical data, SARS-CoV has a life cycle of less than 24 hours. Virus particles can affect host cells and then release thousands of offspring in less than a day. Eventually, the virus caused cell membrane rearrangements and multiple cells to fuse together. This can cause enough damage to host tissues, disrupting the immune system and triggering a symptomatic response when the patient begins to fight off the infection. The Middle East Respiratory Syndrome Coronavirus (MERS-CoV) is another highly pathogenic coronavirus that has emerged after the severe acute respiratory syndrome coronavirus (SARS-CoV), posing a serious challenge to world public health security. Virus invasion to the host begins with the interaction between virus surface proteins and specific receptors on the host cell surface. In MERS-CoV and SARS-CoV, spike proteins on the virus envelope are responsible for binding to receptors, determining the ability of the virus to invade the host, and tissue specificity, and are also important targets for the development of drugs or vaccines to prevent and treat coronavirus-induced diseases. As a type of coronavirus, 2019-nCov not only shows the similar side of the family, but also displays its own characteristics in the incubation period and infectivity. Clinical studies show that compared with SARS-CoV and MERS-CoV, 2019-nCov can survive 5 days under suitable environmental conditions, and the incubation period after entering the human body can be as long as 14 days, and during this incubation period, it seems that some patients can The virus continues to spread. Further investigation revealed that 2019-nCoV can infect non-sensitive cells overexpressing human ACE2 (angiotensin-converting enzyme, cell receptor for SARS-CoV), suggesting that 2019-nCoV can use SARS-CoV receptors to invade cells. In addition, because it has 96% similarity to the entire genome of bat virus TG13, it plays a role as an intermediate host in bats during its transmission pathway. As of this writing, the host that specifically caused the outbreak has not been found, and the long-latency and strong infectious mechanisms of 2019-nCov have not yet been elucidated. These require further research by researchers.

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