Strikingly, SARS CoV-2 S harbors a furin cleavage site at the S1/S2 boundary, which is processed during biosynthesis. The presence of a furin cleavage site sets SARS-CoV-2 S apart from SARS-CoV S (and SARSr-CoV S) that possesses a monobasic S1/S2 cleavage site processed upon entry of target cells. The investigation speculate that the almost ubiquitous expression of furin-like proteases could participate in expanding SARS-CoV-2 cell and tissue tropism, relative to SARS-CoV, as well as increasing its transmissibility and/or altering its pathogenicity.