Both recombinant RVFV strains inoculated i.p. were able to kill Ifnar1-deficient 129S2/SvPas mice within 2 days whereas wild-type 129S2/SvPas mice survived infection, indicating that a functional IFN-α/β pathway is critical for the protection of mice from fatal infection with these attenuated viruses. The gene discussed is IFNAR1; the disease is infection.