ACE2 and COVID-19: The important role played by the nasal epithelia in COVID-19 has been further magnified after the emergence of the many Omicron sublineages, which exhibit highly efficient replication within the nasal mucosa; furthermore, Angiotensin converting enzyme 2 (ACE2) and trans-membrane protease serine 2 (TMPRSS2), the primary entry factors of SARS-CoV-2, are expressed in a wide range of human mucosal surfaces of the head and neck, most prominently in the nasal cavity and trachea (17).