ACE2 and COVID-19: In COVID-19, age seems to be the most important determinant of infection risk possibly reflecting age-related reduction in expression of angiotensin-converting enzyme 2 (ACE-2) receptor, a cellular receptor for SARS- CoV-2 binding [30] age-dependent difficulty in removing particles from small airways [31], excessive release of inflammatory mediators in elderly “inflammaging” [32], incompetent immune response, and high frequency of comorbidities in the elderly population [33].