TMPRSS2 and COVID-19: Genetic association studies have demonstrated that genetic variations influencing SARS-CoV-2 receptors, such as angiotensin-converting enzymes or transmembrane serine protease-2 and immune components (interferons, interleukins, toll-like receptors, and human leukocyte antigen), are essential host determinants associated with the severity of COVID-19 [6,7].