Structure and genome of severe acute respiratory syndrome coronavirus 2

Abstract

SARS-CoV-2 is a novel coronavirus responsible for the current COVID-19 pandemic. It is the seventh coronavirus known to infect humans (the previous human coronaviruses are HCoV-OC43, HCoV-229E, HCoV-HKU1, HCoV-NL63, SARS-CoV and MERS-CoV) and the third human coronavirus known to cause severe illness in human after SARS-CoV and MERS-CoV. These three coronaviruses have caused three different severe respiratory diseases outbreaks within the last two decades: SARS in 2002-2003, MERS in 2012 and COVID-19 in 2020. The aim of this review was to summarize information on the genome and structure of SARS-CoV-2.    SARS-CoV-2 is an enveloped positive-sense single-stranded RNA virus with a crown-like appearance due to the presence of spike glycoprotein on the envelope. The nonsegmented genome of SARS-CoV-2 of approximately 30kb encodes two large polyproteins, four main structural proteins namely spike, membrane, envelope and nucleocapsid proteins as well as several accessory proteins. Analysis of SARS-CoV-2 genome shows that it is highly related to coronavirus from the bat (96%), pangolin (91%) and SARS-CoV (80%). Variants of SARS-CoV-2 have evolved continuously as a result of genetic mutations and are circulating worldwide. These variants have varying degrees of transmissibility, disease severity, susceptibility to therapeutics and detection by diagnostic tools. Understanding the structure and genome of SARS-CoV-2 is important in the control, management, diagnosis and treatment of COVID-19 as well as vaccine development.