Several amino acid substitutions in RBD were identified in the SARS-CoV-2 RBD compared to Bat-SARS-CoVs and SARS-CoV. Mutations in the spike protein could change the tropism of a virus, including new hosts or increasing viral pathogenesis (Shang et al., 2020[13]). HIV infection is a good model of change in viral tropism by mutations in the envelope proteins. These mutations switch co-receptor use (CCR5 to CXCR4) increasing the viral pathogenesis (Mosier 2009[7]). Interestingly, our data showed that these changes are not only related to the ability of interaction with the human ACE2 receptor but also for improving this receptor recognition. The presence of two loops around the RBD of SARS-CoV-2 might be promoting the interaction with the ACE2 receptor, improving the binding to this receptor by increasing the number of atoms involved (Tables 1(Tab. 1) and 2(Tab. 2)). The amino acid substitutions and the longer capping loops could explain the increase in binding affinities in SARS-CoV-2 compared to SARS-CoV (Table 1(Tab. 1)). Higher affinity values might be related to the dynamic of infection and the rapid spread observed for this virus.