TMPRSS2 and influenza: However, because over-expression of TMPRSS2 explains the greater impact of viral diseases (influenza, SARS-CoV, metapneumovirus, MERS) that use ACE-2-receptor/TMPRSS2 for cell binding/cell entry on patients with DS, it is unknown to what extent the increased clinical vulnerability recently observed in DS is specific for COVID-19 [9].