An intuitive evidence is that hypoxia can reduce the incidence of COVID-19, which may be related to the fact that hypoxia can shorten the half-life of SARS-CoV-2 virus and induce down-regulation of angiotensin-converting enzyme 2 (ACE2) expression, thereby increasing the body’s resistance to viruses (Arias-Reyes et al., 2020). Here, ACE2 is linked to COVID-19.