Interestingly, even with a 10-fold higher MOI used for the WT infection of donor Vero-ACE2 cells relative to other variants, we observed comparable rates of cell-to-cell transmission between WT, D614G, B.1.1.7, and B.1.351 (Fig. 7 A, Upper and B and SI Appendix, Fig. S5 A and B). Here, ACE2 is linked to infection.