According to Felsenstein and Hedrich, the reasons for mild manifestations in childhood could depend on cross-reactive antibodies and co-clearance with other viral infections, frequent contact with seasonal coronaviruses, and an increased expression of ACE2 in young people, which can facilitate virus infection but limit inflammation and reduce the risk of serious disease due to its involvement in anti-inflammatory signaling [27]. This evidence concerns the gene ACE2 and viral infectious disease.