H9N2 avian influenza virus (H9N2/G1) is widely prevalent among poultry in various Eurasian regions, including mainland China and Hong Kong. In 1999 and 2003, H9N2 influenza was reported in 3 children in Hong Kong. All 3 of them developed relatively mild symptoms and recovered within a week [5, 6] . The 6 internal genes of H9N2/G1 virus were found to be related to the highly pathogenic avian influenza virus A/Hong Kong/483/97 (H5N1). Although the H9N2/G1 virus was found mainly in poultry, it has the ability to transmit across species, and with its genetic similarity to the highly pathogenic H5N1, it also poses a threat of becoming pandemic [7] .