Anthropogenic factors and the risk of highly pathogenic avian influenza H5N1: prospects from a spatial-based model

Paul, Mathilde; Tavornpanich, Saraya; Abrial, David; Gasqui, Patrick; Charras-Garrido, Myriam; Thanapongtharm, Weerapong; Xiao, Xiangming; Gilbert, Marius; Roger, Francois; Ducrot, Christian

In Southeast Asia, Thailand was affected by HPAI H5N1 early, with the first official report of poultry and human outbreaks on 23 January 2004. By the end of January 2004, 32 provinces throughout the north and several in the south experienced outbreaks in many types of poultry. The disease caused 17 human cases from January 2004 to June 2005 2 . The epidemic peaked during a ''second wave'' with 1 717 outbreaks in poultry. Beginning in early 2004, Thai authorities implemented a control strategy based on the prohibition of vaccination and the use of preemptive culling. Approximately 60 million poultry were culled during the first wave, with stamping-out measures applied inside a 5-km radius around an outbreak. From July 2004, culling was restricted to suspected farms or villages; 3 million poultry were destroyed during the second wave of outbreaks. The movement of poultry and poultry products was also restricted around infected areas and fighting cocks and free-grazing ducks were targeted by control measures. Apart from these control strategies, the Thai authorities strengthened the surveillance of HPAI. In addition to the passive surveillance system and routine laboratory surveillance, the Government implemented an intensive survey known as the ''X-ray campaign'' in October 2004 with 990 000 volunteers conducting door-to-door surveys [23] to check poultry in every house nationwide. From mid-2005, the number of outbreaks in poultry decreased substantially but the occurrence of poultry outbreaks in two provinces of Thailand in late 2008 indicates that the threat of HPAI in Thailand remains present.