A possible COVID-19-driven hydrogen shortfall may perhaps happen due to SARS-CoV-2 infection-driven aggressive inflammatory responses in enterocytes via highly expressed angiotensin-converting enzyme 2 (ACE2) and transmembrane protease serine 2 (TMPRSS2) receptors (Zhang et al., 2021), that eventually affect microbial ecology and dihydrogen production. This evidence concerns the gene ACE2 and COVID-19.