During June 2003, mosquito surveillance was conducted at a US Army installation and a US Military training site 2 km south of the demilitarized zone, Republic of Korea. Mosquitoes were collected using Mosquito MagnetsTM, sorted to species, and assayed for the presence of arboviruses. From the 3,149 mosquitoes that were sorted into126 pools, one Aedes vexan snipponii pool (out of 73 pools) tested positive for flavivirus RNA by reverse transcription-PCR. After isolation from C6/36 cell culture supernatant, the viral genome was sequenced and found to be 98.9% related to Chaoyang virus, a potential arthropod-specific flavivirus. This report details the first identification of Chaoyang virus in the Republic of Korea and highlights its relationship to other flaviviruses
