SARS-Cov-2 (COVID-19; WHO nomenclature), which originated from the city of Wuhan in China, has now spread to at least 175 countries and territories with unexpected societal and economic consequences. Infections with coronaviruses are not new to humans; they usually cause mild respiratory infections especially during winter months. However, to date, there are three recombinant coronaviruses that cause severe illness; SARS (2003, originated in China), MERS (2012, the disease emerged in Saudi Arabia), and 2019 SARSCov- 2 known as COVID-19, it too, originated from China. Due to its rapid and wide global transmission, the WHO declared it as pandemic. Of note, the overall genomic sequence of SARS-Cov-2 differs from other known coronaviruses. Unlike its predecessors, SARS-Cov-2 genome facilitates viral binding to the host cells much more tightly compared to its common host cell receptor - a distinct feature of Spike proteins and the binding process is activated by certain cellular enzymes. It has been estimated about 10% of exposed individuals are asymptomatic carriers of the virus. SARS-Cov-2 replicates in the upper respiratory tract followed by a rapid extension of infection into the lower respiratory tract. While most infections are clinically mild especially in young adults, few cases particularly in elderly and those with comorbid conditions (e.g., primarily diabetes, hypertension, arrhythmias, cancer patients, immunocompromised individuals) present with severe form of infection which can be life-threatening, a condition known as acute respiratory distress syndrome (ARDS), a consequence of dysregulated immune response (cytokine storm syndrome).
