The infection of murine bone marrow-derived macrophage (BMDM) with RVFV strains ZH501 or MP12 resulted in a lower expression of pro-inflammatory cytokines IFN-β, IFN-γ, TNF-α than after infection with recombinant MP12 with an in-frame deletion of 69% of the NSs gene (rMP12-C13). The gene discussed is IFNB1; the disease is infection.