ACE2 and COVID-19: Preliminary studies have also showed that the variations in angiotensin-converting enzyme 2 (ACE2) gene, HLA gene, and ABO blood group gene on hosts and cells were also associated with susceptibility or severity of COVID-19 (Bourgonje et al., 2020; Kaiser, 2020; Ovsyannikova et al., 2020; Severe Covid et al., 2020).