In particular, the SNPs in the host apolipoprotein E (ApoE) [5], angiotensin converting enzyme 1 (ACE1) [6], transmembrane serine protease 2 (TMPRSS2) [7], C-C chemokine receptor type 5 (CCR5) [8] and human leukocyte antigen (HLA) [9] loci have been linked to the susceptibility and/or severity of COVID-19 [10]. The gene discussed is TMPRSS2; the disease is COVID-19.