SARS-CoV-2 progressed from animal-to-human to human-to-human transmission, causing mild to severe sickness and numerous deaths, verifying two criteria for calling COVID-19 a pandemic. The disease's symptoms progress from mild to severe pneumonia to respiratory and multi-visceral failure, which generally kills comorbid individuals quickly. Intensive global research is undertaken to elucidate viral transmission channels and host defensive mechanisms. Due to its high infectious potential, researchers are repurposing antivirals and other potential inhibitors to build effective diagnostics and therapeutics.