IRF9 and pneumonia: We considered the three loci (IRF7, IRF9 and TLR3) for which germline mutations are causal for influenza pneumonia (62–64) and 10 other genes (IFNAR1, IFNAR2, IRF3, IKBKG, STAT1, STAT2, TBK1, TICAM1, TRAF3 and UNC93B1) encoding products biochemically and immunologically connected to the three core genes, for which deleterious genotypes have been shown to underlie other severe viral diseases (61).