基金supported by The Research Grants Council of The HongKong SAR Government (7488/05M) the Research Fund for the Control of Infectious Diseases of the Health, Welfare and Food Bureauof the Hong Kong SAR Government, the Li Ka Shing Foundation+1 种基金the Providence Foundation in memory of The late Dr. Lui Hac Minhgrants from The National Natural Science Foundation of China(30571674, 30771988)~~