Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the coronavirus disease 2019 (COVID-19) pandemic, gains entry into host cells through contact between projected droplets and the cells of the nose, oral cavity, or eyes. SARS-CoV-2 infectivity depends on the ability of the virus to enter host cells.
The virus binds to the host cell receptor, angiotensin-converting enzyme 2 (ACE2), which is abundantly expressed in the epithelial tissue that lines the respiratory tract; it is in this sense that SARS-CoV-2 is primarily considered a respiratory virus. The ACE2 receptor interacts with the viral spike protein, thereby facilitating entry into the cells.
