ACE2 and COVID-19: Coronaviruses are pathogens that largely affect the respiratory system but the expression of host SARS-CoV-2 receptor, angiotensin-converting enzyme 2 (ACE2), is not lung-specific, and its presence in a variety of tissues, including the brain, the intestine, the blood vessels, and the kidney, could subject these organs to direct infection by SARS-CoV-2 making COVID-19 a systemic disease [2].