Among the four structural proteins, that is, the S (spike), E (envelope), M (membrane), and N (nucleocapsid) proteins, the spike protein is responsible for attaching to and fusing with the membrane of a host cell through angiotensin converting enzyme 2 (ACE2) receptor.[4, 5] The receptor‐binding domain (RBD) of S protein exhibits the most variable part of the COVID‐19 genome.[5, 6] Mutations of critical amino acids in RBD may change ACE2 binding affinity and pathology in humans. The gene discussed is ACE2; the disease is COVID-19.