USP18 and viral infectious disease: The up-regulated shared genes include APOL9A, CCL12, CMPK2, DHX58, H28, IFI44, IFIT1, IFIT2, IFIT3, ISG15, MX1, OAS1A, OASL2, RSAD2, RTP4, SLFN3, USP18, XAF1, and ZBP1. These genes are associated with innate immune response to viral infection and were up-regulated in different IAV strains (H1N1, H3N2, H5N1, H5N2, and H7N1) in A549 cells [33], human blood, PBMC, and primary epithelial cells [34].