Modelling the Avian Influenza H5N1 Virus Infection in Human and Analyzing its Evolution in China

Since the first human case of H5N1 avian influenza infection was found in Hong Kong 1997 (Ku and Chan 1999), the cumulative number of confirmed human cases of H5N1 infection reported to the World Health Organization (WHO 2012) to date is 596 in the world and which of 42 HPAI H5N1 human cases in China with 60% mortality. More than 80% of the total HPAI H5N1 human cases have been reported in avian influenza endemic areas, indicating hotspots for bird-to-human transmission (Watanabe et al. 2012). Further, the HA genes of 15 human isolates from Southern China are closely related to each other and to H5N1 poultry viruses isolated in the same geographic location at the same time, suggesting infected domestic poultry as the source of human infections (Shu et al. 2006, Wang et al. 2008). By contrast, the HA gene of one human isolate from the Xinjiang Autonomous Region in Northern China is more closely related to Qinghai Lake-like migratory birds viruses (Neumann et al. 2010). Therefore, many experts expect the occurrence of a pandemic due to a mutant avian influenza virus which can be easily transmitted among humans (Iwami et al. 2009). It is important and urgent to study the infection of HPAI H5N1 virus in human to refine the understanding of HPAI H5N1 virus evolution for better control and prevention of HPAI H5N1 virus transmission.