We considered three loci identified as mutated in patients with life-threatening influenza: TLR3, IRF7, and IRF9. We also considered 10 loci mutated in patients with other viral illnesses but directly connected to the three core genes conferring influenza susceptibility: TICAM1/TRIF, UNC93B1, TRAF3, TBK1, IRF3, and NEMO/IKBKG from the TLR3-dependent type I IFN induction pathway, and IFNAR1, IFNAR2, STAT1, and STAT2 from the IRF7- and IRF9-dependent type I IFN amplification pathway. Here, IRF9 is linked to influenza.