SARS-CoV-2 fusion with cell-plasma membrane and cell entry are therefore initiated by the interaction of the receptor binding domain (RBD) of the S protein to human ACE2 at the cell-surface (Li et al., 2003; Li et al., 2005; Yan et al., 2020a; Wang et al., 2020e; Wan et al., 2020) (Figure 1B, scheme representing key viral and cell molecules involved in virus attachment and fusion with target cell that mediate viral entry and infection). Here, ACE2 is linked to infection.