A team of scientists from the University of Texas, USA, has recently revealed that the P681R spike mutation is responsible for increased infectivity of the delta variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The P681R spike mutation increases the replication of the delta variant by increasing the dissociation of S1 and S2 subunits at the furin cleavage site. The study is currently available on the bioRxiv* preprint server.