The risk factor of a potential infection source for a herd of interest
decreases with decreasing animal density (Ehlers et al., 2003). The
outbreaks in January were concentrated in the central, the southern
part of the Northern and Eastern regions of Thailand which are
wetlands, water reservoirs and dense poultry areas (Tiensin et al.,
2005).The areas at risk of infection include those of shorter distance
to poultry farm, to wetlands and to rice paddies. The consistent
dissemination of infection was confined to backyard chicken and
ducks raising on the wetland. In addition the vicinity to commercial
poultry productions is high risk of HPAI infection. The commercial
poultry productions encompass market, slaughterhouse and cockpit
which facilitate the virus transmission.