State Key Laboratory of Emerging Infectious Diseases, Department of Microbiology, Li Ka Shing Faculty of Medicine, The Unversity of Hong Kong, 21 Sassoon Road, Pokfulam Road, Hong Kong SAR.
Abstracts of the papers presented at the International Conference of Indian Virological Society on “Emerging and Re-emerging viral Diseases of the Tropics and Subtropics” at Indian Agricultural Research Institute, New Delhi, India, December 11–14, 2007.
The development of highly pathogenic avian influenza A (H5N1) viruses in poultry accompanied with increased human infection in 2006/2007, suggests that the virus has not been effectively contained and that the pandemic threat persists. Systematic surveillance in live-poultry markets conducted over the last seven years in southern China has provided a comprehensive view of the ecology and evolution of H5N1 influenza viruses. Genetic and antigenic analyses have demonstrated the dynamic evolution in this region, with repeated introductions from China to neighboring regions, including Cambodia, Indonesia, Laos, Malaysia, Thailand, and Vietnam. A dramatic spread of the virus westwards throughout Eurasia was also seen after detection of an initial outbreak in wild birds at Qinghai Lake in Central China, in line with our predictions. Genetic analyses revealed that after the H5N1 influenza viruses had established and been endemic several years, they developed into regionally distinct sublineages that allowed us to further trace their transmission pathways. Recent data revealed the emergence and predominance of a single H5N1 virus sublineage in poultry since late 2005 that has gradually replaced those previously detected multiple regional distinct sublineages in China. These viruses have already transmitted to neighboring regions thereby resulting in a new transmission and outbreak wave in South-east Asia. The persistence of H5N1 virus over a large geographical region since its first detection, along with repeated disease outbreaks in both poultry and humans indicates that it will be a long-term and difficult task to bring this virus under control in the absence of well developed disease control systems.
