Several clinical and pre-clinical investigations support this concept: IAV infection is a recognised risk factors for “typical” ARDS [54]; plasma of patients with severe influenza have increased circulating ACE2 levels [55]; and mouse models of influenza-induced lung injury are worsened in Ace2-knockout animals [55] and alleviated by administration of recombinant ACE2 [17]. This evidence concerns the gene ACE2 and influenza.