It is suggested that there is a complex interplay between COVID-19 and the renin-angiotensin-aldosterone system (RAS), in which SARS-CoV-2 has a spike protein receptor-binding domain with high affinity for human angiotensin-converting enzyme 2 (ACE2) (Andersen et al., 2020), which regulate both the cross-species and human-to-human transmission of the virus. This evidence concerns the gene ACE2 and COVID-19.