Considering the analogy between the nucleic acid sequence and ACE-2 binding capability of the aforementioned virus and the novel coronavirus [38,39,40], the observed variation in susceptibility of blood groups A and O for COVID-19 could be related to the existence of natural anti-blood group antibodies in the blood, especially the anti-A antibody in case of O blood group. The gene discussed is ACE2; the disease is COVID-19.