In 2009, a total of 6,646 mosquito pools† from 351 counties in 40 states and DC were reported as testing positive for WNV. Among the WNV-positive pools, 4,987 (75%) had species of Culex mosquitoes thought to be the principal vectors of WNV (e.g., Culex pipiens, Culex quinquefasciatus, Culex restuans, Culex salinarius, and Culex tarsalis). Unidentified or other species of Culex mosquitoes made up 1,488 (22%) pools, and non- Culex mosquito species (e.g., Aedes sp., Anopheles sp., Coquillettidiaperturbans, Culiseta sp., Mansonia titillans, Psorophora columbiae, and Uranotaeniasapphirina) made up 171 (3%) pools. Data from 2009 also included the first report of WNV infection in Aedesepactius, which was collected in Texas. The number of reported WNV-infected mosquito pools peaked during mid-August.