Epidemiology and Control of H5N1 Avian Influenza in China

H5N1, the highly pathogenic avian influenza virus, was first detected in a goose in the Guangdong Province of China in 1996. Multiple genotypes of H5N1 viruses have been identified from apparently healthy waterfowl since 1999. In the years 2004, 2005, and 2006, there were 50, 31, and 10 outbreaks in domestic poultry, respectively. These outbreaks occurred in 23 provinces and caused severe economic damage for the poultry industry in China. A culling plus vaccination strategy has been implemented for the control of epidemics beginning in 2004. Since that time, over 34,000,000 poultry have been depopulated, and over 20 billion doses of the different vaccines have been used to control outbreaks. Although it is logistically impossible to vaccinate every single bird in China due to the large poultry population and the complicated rearing styles, there is no doubt that the increased vaccination coverage has resulted in decreased disease epidemic and environmental virus loading. The experience in China suggests that vaccination has played important roles in the protection of poultry from H5N1 virus infection, the reduction of virus load in the environment, and the prevention of H5N1 virus transmission from poultry to humans.