This furin-like cleavage site is unique to the S protein of SARS-CoV-2 and may, together with the particularly high binding affinity to the target receptor and the peculiarity of a long symptom-free but nevertheless highly infectious time period between infection and appearance of first symptoms or asymptomatic transmission, be responsible for the particularly efficient spread of SARS-CoV-2 compared to previous pathogenic hCoVs [14]. Here, PROS1 is linked to infection.