For analysis of viremia, serum was separated (BD Microtainer tube SST) and RNA was extracted as previously described [8] . WNV RNA copy number was measured by RT-quantitative PCR (RT-qPCR) as previously described [63] . For cultured cells, total RNA was extracted using the RNeasy kit (Qiagen), DNase treated (Ambion) and evaluated for ISG49, ISG56, IFN-b, RIG-I, and MDA5 RNA expression by one-step SYBR Green RT-qPCR. Specific primer sets for ISG-49, ISG-56, RIG-I, and IFN-b have been described previously [30, 64] . Primer sets for MDA5 are: 59-GTGGTCGAGCCAGAGCTGAT and 39-TGTCTCATG-TTCGATAACTCCTGAA.