Genetic Path of the Emergence of SARS-CoV-2

Abstract

Context: Severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) is the seventh coronavirus that has humans as the host. Because of its highly infectious nature, toward the end of January 2020, the WHO declared it a public health emergency of international concern. The present review is about understanding the journey of SARS-CoV-2 to its present form with an attempt to assess the genetic basis of its pandemic-causing abilities. Evidence Acquisition: The data for the present review were accessed through different publications and preprint repositories. Results: SARS-CoV-2 is a beta-coronavirus, and is approximately 60 - 140 nm in size. The appearance of its structure as a crown shape under an electron microscope led to the coining of its name ‘Coronavirus’. Comparative genome and proteome analysis exhibits similarities and differences with reference to SARS-CoV. The open reading frames (ORFs) found on the SARS-CoV-2 genome, and their corresponding proteins have been discussed. Bats may act as reservoir hosts but not exclusively. The possibility of snakes as the host, as well as other intermediate hosts, before reaching humans seems plausible. This has been supported by ACE2 receptor diversity and conservation across different tissues and organisms. The role of spike glycoprotein and its interaction with the receptor through specific residues for invading host cells makes a perfect therapeutic target, but the variations therein and the resulting impact on interactions pose challenges for the same. Conclusions: Though the differences between the MERS, SARS-CoV, and SARS-CoV-2 genomes indicate amino acid changes, leading to the present pandemic situation, the fact that new variants are still emerging signifies that the journey is an ongoing one, which requires monitoring.