COVID-19 : history, pathogenesis and host immune response.

Abstract

By the end of 2019, a pneumonia of unknown etiology occurred in Wuhan, China. Local hospitals started receiving patients presenting symptoms like dry cough, fatigue, and breathing difficulties, most of these patients were linked to the Huanan seafood market, Wuhan, China. The pandemic was afterward confirmed to be associated to a novel coronavirus. The virus spread quickly from Wuhan to other provinces of china, then from china to the rest of the world causing thereby one of the most brutal pandemics in world’s history. SARS-CoV2 has a long incubation period ranging from 3 to 7 days and can go up to 14 days in some cases which makes the infection difficult to be detected early and subsequently the disease spread harder to be controlled. SARS-CoV-2 is a single stranded RNA virus with 4 main structural proteins, the spike (S) glycoprotein, the small envelope (E) glycoprotein, the membrane (M) glycoprotein as well as the nucleocapsid (N) protein. Current knowledge about the virus shows that it uses its spike protein to invade host cells, mainly the alveolar epithelial cells. The lung is the most targeted organ among many other organs like heart, small intestine and kidneys that are vulnerable to SARS-CoV-2 infection. The COVID-19 is known to be mild in most cases, but in some cases, it can be severe or even fatal. In the severe cases, acute respiratory distress syndrome was reported, and the capability of SARS-CoV-2 to infect many organs can lead to multiorgan failure and death. SARS-CoV-2 invasion induces several immune responses that could be efficient for infection clearance in mild cases, while in severe cases, the immune response dysfunctions can even contribute to the disease aggravation. Neither the pathogenic mechanism by which SARS-CoV-2 infects host cells, nor the host immune response to its infection have been fully understood, hence further studies are needed to give further evidences about these two phenomena.

Keywords

• covid-19
• sars-cov-2
• coronavirus
• structural proteins
• immune response?