Any process in which a virus stops, prevents, or reduces the activity of host IRF3 (interferon regulatory factor-3), a transcription factor in the RIG-I/MDA-5 signaling pathway. Viral infection triggers phosphorylation of cytoplasmic IRF3, which allows IRF3 to form a homodimer, migrate to the nucleus, and activate transcription of IFN-alpha and IFN-beta genes.