ACE2 and infection: Furthermore, SARS-CoV-2 enters host cells using the receptor angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2) as same as SARS-CoV [32], but they alone cannot explain the significant differences in the primary infection sites and clinical manifestations exhibited by SARS-CoV-2 and SARS-CoV, suggesting the involvement of other receptors in SARS-CoV-2 host interactions [33, 34].