It is thought that cytokine storm mediates many of the systemic effects in severe COVID-19, although viremia may also play a role, as viral RNA has been found in fecal samples and blood (Young et al. 2020; Guo et al. 2020b), and a variety of tissues express high levels of the principal viral receptor, angiotensin-converting enzyme-2 (ACE2) (Qi et al. 2020) and thus may be permissive to viral infection and replication. This evidence concerns the gene ACE2 and viral infectious disease.