Other authors lingered on the spike (S) envelope protein of the currently emerging virus (CoV) inducing severe acute respiratory syndrome (SARS) to explain the crucial role of glycoprotein in infection initiation by binding receptor-binding domain of S protein to the cellular receptor ACE2 and in the phase of viral envelope fusion with the host-cell membrane through the endosomal pathway [44]. This evidence concerns the gene PROS1 and severe acute respiratory syndrome.