Temporal and spatial characteristics of highly pathogenic avian influenza outbreaks in China during 2004 to 2015
Identifying the temporal and spatial characteristics of highly pathogenic avian influenza (HPAI) outbreaks is very important for developing effective and appropriate countermeasures against HPAI and promoting sustainable development in the poultry industry. This study aimed to analyze four aspects of the temporal and spatial characteristics of HPAI outbreaks in China, including the frequency of HPAI outbreaks, numbers of dead animals (died or culled), types of HPAI viruses, and species of infected animals. Temporal characteristics showed that the frequency of HPAI outbreaks decreased and then increased, with some years deviating from the main trend in 2004 to 2010 and 2011 to 2015, while the largest number of dead animals due to HPAI outbreaks was in 2005. During 2004 to 2015, HPAI H5N1 was the major type of HPAI virus, and chickens had the greatest risk of being infected with HPAI, followed by ducks and geese. The HPAI outbreaks had obvious seasonal effects clustered in January to February, June, and November. Spatial characteristics revealed that outbreaks were more frequent in Xinjiang, Hubei, and Guangdong but caused a larger number of dead animals in Liaoning and Shanxi. HPAI H5N1 appeared in 25 provinces, while HPAI H5N2 was mainly localized in Hebei and Jiangsu, and HPAI H5N6 occurred in Heilongjiang, Jiangsu, Hunan, and Guangdong. HPAI viruses were most frequently detected in chickens and wild birds in northern China, while the majority of HPAI infections were identified in chickens, ducks, and geese in southern China. Regionally, HPAI outbreaks were most frequent in the western region but resulted in larger number of animals dying or being culled in the eastern region. These findings could provide a new understanding of the distributional characteristics of HPAI outbreaks and offer prospects for better prevention and control strategies.