Professor Chen Honglin (middle in the first row), Professor of State Key Laboratory for Emerging Infectious Diseases and Department of Microbiology, Li Ka Shing Faculty of Medicine, HKU, and the research team. The outbreak of H7N9 avian influenza virus was first reported in mainland China in 2013. Human cases of H7N9 have surged in several Provinces since the autumn of 2016, causing over 500 case