In contrast, since SARS-CoV-2 enters the body via the oral cavity and oropharynx, where epithelial cells that express the angiotensin-converting enzyme-2 (ACE2) and transmembrane protease serine 2 (TMPRSS2) virus receptors are found [18], critical mutual interactions between the resident oral microbiome and the virus exist, which favors the oral dysbiosis and/or the establishment of the viral infection and disease progression [1,4,5]. The gene discussed is ACE2; the disease is viral infectious disease.