IRF3 and infection: In the absence of IRF-3, significantly higher levels of viral RNA were observed by days 2 and 4 after infection in serum (10.6-fold, p < 0.0001; and 4.8-fold, p < 0.0001; Figure 1B) and draining popliteal lymph nodes (2.2-fold, p = 0.03; and 5.3-fold, p = 0.02; Figure 1C).