title: Seroprevalence to avian influenza A(H7N9) virus among poultry workers and the general population in southern China: a longitudinal study.
abstract: BACKGROUND
  Confirmed cases of avian influenza A(H7N9) virus infection in humans continue to occur in mainland China. Few confirmed cases have occurred in poultry workers despite potentially higher rates of exposure.
  
  
  METHODS
  A serological survey was conducted in May and December 2013 in poultry market workers, and in March and September 2013 in the general population. Blood samples were collected and tested for antibodies to H7N9 and H5N1 viruses by hemagglutination inhibition (HI) assays. Multivariable analysis was employed to identify risk factors related to H7N9 infection indicated by serology among poultry workers.
  
  
  RESULTS
  In the poultry workers, 36 of 501 (7.2%) in May and 56 of 375 (14.9%) in December had HI antibody titers ≥1:160 to H7N9. Of 96 individuals who participated in both surveys, 52 (54.2%) workers had a ≥4-fold rise in H7N9 antibody titers from May to December. In a multivariable analysis, female sex (odds ratio [OR], 2.713; 95% confidence interval [CI], 1.098-6.705) and ≥10 years of occupational exposure (OR, 3.592; 95% CI, 1.246-10.354) were identified as risk factors for infection. Seroprevalence against H5N1 at ≥1:160 was low in May (4/501 [0.8%]) and December (3/375 [0.8%]). In the general population, 0 of 417 individuals in March and 0 of 408 individuals in September had antibody titers ≥1:160 to H7N9 or to H5N1.
  
  
  CONCLUSIONS
  Although none of the participants in our study had virologically confirmed H7N9 infection, the high proportion of poultry workers with serologic evidence of H7N9 infection between May and December 2013 suggests a substantial risk of mild H7N9 infections in this group, supporting stricter control measures in live poultry markets.
authors.affiliation: Major Infectious Disease Control Key Laboratory, Key Reference Laboratory of Pathogen and Biosafety, Shenzhen Center for Disease Control and Prevention, Shenzhen, People's Republic of China.
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.affiliation: Major Infectious Disease Control Key Laboratory, Key Reference Laboratory of Pathogen and Biosafety, Shenzhen Center for Disease Control and Prevention, Shenzhen, People's Republic of China.
authors.forename: Shisong
authors.initials: S
authors.lastname: Fang
authors.affiliation: Major Infectious Disease Control Key Laboratory, Key Reference Laboratory of Pathogen and Biosafety, Shenzhen Center for Disease Control and Prevention, Shenzhen, People's Republic of China.
authors.forename: Xing
authors.initials: X
authors.lastname: Lu
authors.affiliation: Division of Epidemiology and Biostatistics, School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China.
authors.forename: Cuiling
authors.initials: C
authors.lastname: Xu
authors.affiliation: Division of Epidemiology and Biostatistics, School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China.
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Cowling
authors.affiliation: Major Infectious Disease Control Key Laboratory, Key Reference Laboratory of Pathogen and Biosafety, Shenzhen Center for Disease Control and Prevention, Shenzhen, People's Republic of China.
authors.forename: Xiujuan
authors.initials: X
authors.lastname: Tang
authors.affiliation: Major Infectious Disease Control Key Laboratory, Key Reference Laboratory of Pathogen and Biosafety, Shenzhen Center for Disease Control and Prevention, Shenzhen, People's Republic of China.
authors.forename: Bo
authors.initials: B
authors.lastname: Peng
authors.affiliation: Major Infectious Disease Control Key Laboratory, Key Reference Laboratory of Pathogen and Biosafety, Shenzhen Center for Disease Control and Prevention, Shenzhen, People's Republic of China.
authors.forename: Weihua
authors.initials: W
authors.lastname: Wu
authors.affiliation: Major Infectious Disease Control Key Laboratory, Key Reference Laboratory of Pathogen and Biosafety, Shenzhen Center for Disease Control and Prevention, Shenzhen, People's Republic of China.
authors.forename: Jianfan
authors.initials: J
authors.lastname: He
authors.affiliation: Major Infectious Disease Control Key Laboratory, Key Reference Laboratory of Pathogen and Biosafety, Shenzhen Center for Disease Control and Prevention, Shenzhen, People's Republic of China.
authors.forename: Yijun
authors.initials: Y
authors.lastname: Tang
authors.affiliation: Major Infectious Disease Control Key Laboratory, Key Reference Laboratory of Pathogen and Biosafety, Shenzhen Center for Disease Control and Prevention, Shenzhen, People's Republic of China.
authors.forename: Xu
authors.initials: X
authors.lastname: Xie
authors.affiliation: Major Infectious Disease Control Key Laboratory, Key Reference Laboratory of Pathogen and Biosafety, Shenzhen Center for Disease Control and Prevention, Shenzhen, People's Republic of China.
authors.forename: Shujiang
authors.initials: S
authors.lastname: Mei
authors.affiliation: Major Infectious Disease Control Key Laboratory, Key Reference Laboratory of Pathogen and Biosafety, Shenzhen Center for Disease Control and Prevention, Shenzhen, People's Republic of China.
authors.forename: Dongfeng
authors.initials: D
authors.lastname: Kong
authors.affiliation: Major Infectious Disease Control Key Laboratory, Key Reference Laboratory of Pathogen and Biosafety, Shenzhen Center for Disease Control and Prevention, Shenzhen, People's Republic of China.
authors.forename: Renli
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Major Infectious Disease Control Key Laboratory, Key Reference Laboratory of Pathogen and Biosafety, Shenzhen Center for Disease Control and Prevention, Shenzhen, People's Republic of China.
authors.forename: Hanwu
authors.initials: H
authors.lastname: Ma
authors.affiliation: Major Infectious Disease Control Key Laboratory, Key Reference Laboratory of Pathogen and Biosafety, Shenzhen Center for Disease Control and Prevention, Shenzhen, People's Republic of China.
authors.forename: Jinquan
authors.initials: J
authors.lastname: Cheng
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000383:Agriculture; D000914:Antibodies, Viral / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D062306:Geography, Medical; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D053124:Influenza A Virus, H5N1 Subtype / Q000276:immunology; D064766:Influenza A Virus, H7N9 Subtype / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology* / Q000276:immunology; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance; D016036:Seroepidemiologic Studies; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral
keywords: influenza A(H7N9); poultry workers; seroprevalence