To begin to define how an IRF-1 deficiency increased the susceptibility of mice to WNV infection, we measured viral burden by fluorogenic quantitative RT-PCR or viral plaque assay at days 1, 2, 4, 6 and 8 post infection in serum, peripheral organs (draining lymph nodes, spleen and kidney) and the CNS (brain and spinal cord). Here, IRF1 is linked to infection.