The endothelium was quickly identified as central to the vascular effects associated with COVID-19, not only because of the intimate proximity of alveolar epithelial and endothelial cells to facilitate efficient gas exchange, but also because endothelial cells express ACE2 and are highly regulated by many of the mediators that are modulated by changes in ACE2 presence or activity. This evidence concerns the gene ACE2 and COVID-19.