Answer:
the proteins on its surface and that of the host
Explanation:
The process of viral infection begins with the entry of the virus to its host cells. For this purpose, viral surface proteins attach to receptor proteins found on target host cells. For example, the coronavirus responsible for the pandemic contains spike (S) proteins on its surface that bind to angiotensin-converting enzyme 2 (ACE2) receptors and thus infects host target cells. Moreover, the specificity of the binding determines the ability to infect and the host range of the viruses. In the case of coronavirus, it has been suggested that ACE2 receptors are not fully developed in children, thereby children would be less susceptible to viral infection.
