Based on the aforementioned data correlating the binding affinity of SARS-CoV for hACE2 with the rate of transmissibility , viral replication in distinct species, and disease severity, the investigation thypothesize that the most pathogenic coronaviruses will exhibit S glycoprotein trimers spontaneously sampling closed and open conformations, as is the case for SARS-CoV-2, SARS-CoV and MERS-CoV.