title: Potential infections of H5N1 and H9N2 avian influenza do exist in Guangdong populations of China.
abstract: BACKGROUND
  Southeast China is one of the sites of influenza origin. During 2003--2004, nine avian influenza outbreaks took place in Guangdong Province. But no human case was reported. To examine the status of potential human infection by human influenza (H1N1, H3N2) and avian influenza (H5N1, H7N7, H9N2) in the avian influenza epidemic area of Guangdong Province, China, we conducted a seroepidemiologic survey in the people of this area from April to June of 2004.
  
  
  METHODS
  Three out of 9 H5N1 avian influenza affected poultry areas in Guangdong were randomly selected, and the population living within 3 kilometers of the affected poultries were chosen as the survey subjects. One thousand two hundred and fourteen people were selected from 3 villages at random. Human and avian influenza antibody titers were determined by hemagglutination-inhibition (HI) test and microneutralization test (MNT).
  
  
  RESULTS
  The positive rate of antibody to H5N1 was 3.03% in the occupational exposure group and 2.34% in general citizens group; that of H9N2 was 9.52% in the occupational exposure group and 3.76% in the general citizens group. Moreover one case in the occupational exposure group was positive for H7N7. One year later, all previously positive cases had become negative except for one H5N1-positive case.
  
  
  CONCLUSIONS
  The observations imply that H5N1 and H9N2 avian influenza silent infections exist in Guangdong populations.
authors.affiliation: School of Public Health, Sun Yat-sen University, Guangzhou, Guangdong 510080, China.
authors.forename: Ci-yong
authors.initials: CY
authors.lastname: Lu
authors.forename: Jia-hai
authors.initials: JH
authors.lastname: Lu
authors.forename: Wei-qing
authors.initials: WQ
authors.lastname: Chen
authors.forename: Li-fang
authors.initials: LF
authors.lastname: Jiang
authors.forename: Bing-yan
authors.initials: BY
authors.lastname: Tan
authors.forename: Wen-hua
authors.initials: WH
authors.lastname: Ling
authors.forename: Bo-jian
authors.initials: BJ
authors.lastname: Zheng
authors.forename: Hong-yan
authors.initials: HY
authors.lastname: Sui
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D002645:Chickens; D002681:China / Q000453:epidemiology; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D053124:Influenza A Virus, H5N1 Subtype; D053127:Influenza A Virus, H9N2 Subtype; D005585:Influenza in Birds / Q000453:epidemiology; D007251:Influenza, Human / Q000453:epidemiology*; D008875:Middle Aged; D009500:Neutralization Tests; D016273:Occupational Exposure