Mechanism and transmission routes of COVID-19

A recent form of novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which has emerged in China, appears to have a distinct genome from the previously sequenced coronavirus. SARS-CoV-2 is shown to cause acute respiratory infections in humans. SARS-CoV-2 is a ribonucleic acid virus believed to have transmitted from a zoonotic host accompanied by human-to-human spread that has contributed to a recent pandemic. Clinical symptoms of coronavirus disease 2019 patients start with tiredness, sore throat, cough, running nose, and fever, and then progressing to trouble breathing and loss of taste; severe cases experience death due to organ failure. Also, a few affected individuals can also be asymptomatic. Elderly and individuals with chronic conditions viz. hypertension, diabetes, and cardiac complications are more vulnerable to viral infection and disease severity. In this chapter, we discuss in detail the origin of SARS-CoV-2, followed by the various risk factors that could influence the infection, and finally the different modes of viral transmission.