ACE2 and COVID-19: Furthermore, the cell entry receptor for COVID-19 is the angiotensin-converting enzyme-2 (ACE-2) receptor, which is mainly located on type 2 pneumocytes rather than in the upper respiratory tract, which could occasionally lead to false-negative results for oropharyngeal or nasopharyngeal swab tests due to the lower viral load in these specimens [5,7,11].