The only five humanized single domain antibodies (nanobodies), 1E2, 2F2, 3F11, 4D8, and 5F8, obtained from phage display neutralize WT and PT SARS-CoV-2 by targeting residues on ACE2 binding site and prevent against both virus infection types through a direct blocking of RBD-ACE2 binding. The gene discussed is ACE2; the disease is viral infectious disease.