ACE2 and COVID-19: It has been established that SARS-CoV-2 can upregulate the expression of the type 2 angiotensin converting enzyme (ACE-2), and can bind ACE-2 receptors on the surface of the host cells for cell entrance in many organs, which may explain the comorbidities we observed in COVID-19 patients, such as hypertension, diabetes and COPD [29–31].