Moreover, the association between VD and Covid-19 may depend on angiotensin converting enzyme 2 (ACE2), the main host cell receptor for SARS-CoV2 [33] and a fundamental component of the renin-angiotensin-aldosterone system (RAAS) [34], the latter relevant for pulmonary, cardiovascular and kidney function. The gene discussed is ACE2; the disease is sexually transmitted disease.