[Virological and serological surveys for H9N2 subtype of influenza A virus in chickens and men in Shenzhen city].

OBJECTIVE: To understand the distribution of influenza A H9N2 virus in chickens and men in Shenzhen area. METHODS: Virus isolation was performed in embryonated hen s eggs with routine method. The antibody to H9N2 virus was detected with micro-hemagglutination inhibition (HI) test, then the results were checked by using the neutralization assay in MDCK cells. RESULTS: Totally 27 strains of influenza A H9N2 virus were isolated from chickens in farm markets in Shenzhen, whereas no H9N2 virus was isolated from men. Approximately 26% of human sera with the HI titers > or =20 to H9N2 virus were detected. However only 7% of chicken sera with the HI titers > or =20 to H9N2 virus were detected. Meanwhile the HI titer and (MGT) of antibody to H9N2 virus in human sera increased with age. It was also found that there was a close relationship between HI antibody titer to H9N2 virus in human sera and occupation. CONCLUSIONS: The distribution of influenza A H9N2 virus in chicken and men in Shenzhen was rather wide. The human H9N2 virus infection probably derived from chicken H9N2 virus.