Detection of flavivirus seroconversions in sentinel chicken flocks located in four Australian states are used to provide an early warning of increased levels of Murray Valley encephalitis virus (MVEV) and Kunjin virus (KUNV) activity in the region. During the 2003–2004 season low levels of flavivirus activity were detected in northern Australia with both MVEV and KUNV virus activity detected in the Kimberley and Pilbara regions of Western Australia and in the Northern Territory. A single case of Murray Valley encephalitis was reported from Central Australia. MVEV activity was also detected at
Minindee in western New South Wales for the first time since 2000–2001. No activity was detected in
Victoria.