ACE2 and viral pneumonia: While COVID-19 is typically characterized by symptoms of viral pneumonia, SARS-CoV-2 causes a systemic disease, with possible involvement of the heart, liver, pancreas, and kidneys, as well as alterations in circulating lymphocytes and the immune system, because of the ubiquitous distribution of the main viral entry receptor, namely angiotensin converting enzyme 2 (ACE2) (2, 9, 10).