The Evolution Of H9N2 Subtype Avian Influenza Virus In Mainland China

The hemagglutinins of 30 H9 subtype Avian Influenza Viruses (AIVs) isolates from the domestic chickens among different geographical areas in mainland China during the period of 1994 to 2001 were analyzed antigenically and genetically.Hemagglutinins Inhibition (HI) testes showed that there were obvious variations among the isolates from different geographical areas. This result explained why the protection rates of current vaccine were different around the country.DNA sequence analysis of H9 hemagglutinin genes showed that these viruses were closely related and possibly came from one source. Phylogenetic analysis of these isolates revealed that they were similar to the two isolates, which came from the Hong Kong poultry markets in 1997, A/chicken/Hong Kong/G9/97 and A/duck/Hong Kong/y280/97 respectively. None of the isolates from mainland China had multiple basic amino acid at HA cleavage site that confer high pathogenicity to some H5 and H7 ATVs. The deduced amino acid sequence revealed that the isolates from Guangdong Province possibly were the primary source of AFVs of mainland China. The central China area, such as Henan Province, may be a secondary source to the north and west of China. ATVs changed by and by in the south district of mainland China, just like Nan Jing and Shanghai.In one word the hemagglutinins of H9 subtype avian influenza virus strains in mainland China reflect the geographical paramenters in one way.