. "Any process in which a virus stops, prevents, or reduces the activity of host IRF9 (interferon regulatory factor-9), a transcription factor involved in the innate immune response. Viral infection triggers phosphorylation of cytoplasmic IRF9 bound to STAT1 and STAT2, forming the ISGF3 complex. The ISGF3 complex migrates to the nucleus and activates transcription of IFN-responsive genes." . . . . "suppression by virus of host IRF9 activity" . "inhibition of host interferon regulatory factor-9 by virus" . "inhibition of host IRF9 by virus" . . .