Besides, ACE2 also was thought to have higher expression in germ cells of males when compared with females (Sama et al., 2020), and smoking males accounted for nearly 50% in rural areas of China while approximately 44.8% overall (Zhi et al., 2019), suggesting possibly that males were more prone than females to be at the risk of COVID-19, which were consistent with our study. This evidence concerns the gene ACE2 and COVID-19.