Several reasonable hypotheses have been proposed to explain this phenomenon, such as specific drug therapies, azithromycin (anti-inflammatory effect) and DNase (mucolytic effect), characteristics of the CF cohort (younger age, shielding, and protective self-isolation), alteration of intracellular ions that negatively affects virus replication, and lower levels of IL-6 and the cellular protease TMPRSS2 that SARS-CoV-2 uses to enter target cells. The gene discussed is TMPRSS2; the disease is cystic fibrosis.