Fig. 2.

Potential factors influencing the variability of coronavirus disease-2019 (COVID-19). Factors influencing severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection penetrance and disease course remain unclear. Several factors are hypothesized to influence the clinical phenotype and illness severity of COVID-19 including the presence of a coinfection, environmental factors, host factors, host genetics, and viral factors, among others. ACE2, angiotensin-converting enzyme 2; ADAM17, ADAM metallopeptidase domain 17; CV, cardiovascular; ICU, intensive care unit; TMPRSS2, transmembrane serine protease 2.