The Origin, Transmission, and Clinical Therapies in the Management of Coronavirus Diseases

ABSTRACT

A brief history of the human coronaviruses (HCoVs) tells us that they are inherently zoonotic in origin. The molecular analysis of these HCoVs revealed a large genome of approximately 30 kb that encodes for a fixed subset of structural proteins, non-structural proteins, and varied accessory proteins. Additionally, the HCoV genomes have a prerequisite ability to undergo mutation and recombination that fosters advantageous gene gain and gene losses. A culmination of all these factors has led to the evolution of HCoVs that can cause mild infections as well as the global pandemic COVID-19. Using simplified phylogenetic trees, we elucidate the probable primary zoonotic origin and the animal reservoirs for the HCoV family. This chapter aims to highlight the evolution of the common cold triggering HCoV cluster (HCoV-229E, HCoV-NL63, HCoV-OC43, and HCoV-HKU1), as well as the severe epidemic and pandemic causing HCoV cluster (SARS-CoV-1, SARS-CoV-2, and MERS-CoV). The final section of this chapter is dedicated to exploring clinical therapies against the above CoVs. As such the CoV replication pathways are exploited, and a select few repurposed drug candidates, novel agents, and their combination are organized based on the steps they inhibit in this pathway.