Amra korbo Joy (2020)

Human lives are threatened by the outbreak of the novel Coronavirus Disease 2019 (COVID-19). As of 21 March 2020, COVID-19 has affected more than 267 thousand people across 184 countries (World Health Organization 2020). This new coronavirus disease is declared to be a global pandemic by the World Health Organization. Coronavirus represents a large family of viruses that are responsible for the common cold to various respiratory disorders like middle-east respiratory syndrome (MERS), severe acute respiratory syndrome (SARS), etc. These viruses are transmitted typically between animals and humans. There are many known coronaviruses in animals and have not affected humans. COVID-19 virus, also known as the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a new strain of the coronavirus and has recently been identified. COVID-19 virus belongs to the Coronaviridae family, order Nidovirales. It contains mainly four structural proteins: spike (S), envelope (E), membrane (M), and nucleocapsid (N). Spike glycoprotein is responsible for virus infection by promoting attachment with the membrane of the host cell. Tang et al. (2020) have identified two dominant viral strains of COVID-19 viruses as L- and S-types, with a 4% genetic difference. They observed that L-type strains, derived from S-type, are more aggressive with a higher transmission rate.