Origin of COVID-19

Coronavirus is a type of virus that is surrounded by non-segmented, singlestranded, positive-sense RNA genomes that reproduce in the cytoplasm. The size of the coronavirus is usually 80-120 nm. It was discovered in Wuhan, China in December 2019, and it was termed 2019 nCoV or COVID-19. The coronavirus is encased in a lipid bilayer and it possesses several proteins. These proteins are surrounded in the envelope of a virus; whereas, in the viral RNA, N-protein shows interactions and it can be found on the outer surface of the viral particle, forming the nucleocapsid. The spike protein is identified as the leading protein and mediates the entrance inside the host body that would cause SARS-CoV-2syndrome. The spike protein has two spheres namely S1 and S2. The receptor that is attached to the S1 and further S2 is responsible for fusion. In the past, the most severe types of virus which had resulted in large-scale pandemics were SARS (in 2002–2003) which occurred in Guandong Province, China. Meanwhile, Saudi Arabia had experienced the Middle East respiratory syndrome (MERS) in 2012. The virus in the 1960s was commonly identified in birds and mammals; mostly in rats, camels, cats and bats. SARS-CoV-2 causative agents belong to the genus β-Coronavirus. Coronavirus can be classified into four genera such as α, β, γ, and δ coronavirus. Alpha and beta coronaviruses are found in mammals such as bats. Gamma coronaviruses would primarily infect birds and affect mammalians, whereas delta coronaviruses would infect both birds and mammals. This chapter highlights the origin, historical background, the classification of the coronavirus as well as providing the conceptual information on various treatment approaches for COVID-19.