COVID-19 has a significantly higher number of well-defined contact pairs compared to SARS-2002: 52 vs. 28 contacts (with 44 and 20 unique pairs, excluding the ones with similar CFs) were found for RBD–ACE2 of the COVID-19 and SARS-2002, respectively (Figure 2B). The gene discussed is ACE2; the disease is COVID-19.