IFNA1 and infection: Mice deficient in the type I interferon (IFN) response (IFN-α-R−/− mice) are highly susceptible to infection with MVEV by an extraneural route [13]; infection of 6-week-old mice with a low dose of wt rMVEV results in uncontrolled virus growth, a high viremia on day 2 pi and uniform mortality by day 6 pi (Fig. 5a and b).