title: Factors Associated with the Emergence of Highly Pathogenic Avian Influenza A (H5N1) Poultry Outbreaks in China: Evidence from an Epidemiological Investigation in Ningxia, 2012.
abstract: In April 2012, highly pathogenic avian influenza virus of the H5N1 subtype (HPAIV H5N1) emerged in poultry layers in Ningxia. A retrospective case-control study was conducted to identify possible risk factors associated with the emergence of H5N1 infection and describe and quantify the spatial variation in H5N1 infection. A multivariable logistic regression model was used to identify risk factors significantly associated with the presence of infection; residual spatial variation in H5N1 risk unaccounted by the factors included in the multivariable model was investigated using a semivariogram. Our results indicate that HPAIV H5N1-infected farms were three times more likely to improperly dispose farm waste [adjusted OR = 0.37; 95% CI: 0.12-0.82] and five times more likely to have had visitors in their farm within the past month [adjusted OR = 5.47; 95% CI: 1.97-15.64] compared to H5N1-non-infected farms. The variables included in the final multivariable model accounted only 20% for the spatial clustering of H5N1 infection. The average size of a H5N1 cluster was 660 m. Bio-exclusion practices should be strengthened on poultry farms to prevent further emergence of H5N1 infection. For future poultry depopulation, operations should consider H5N1 disease clusters to be as large as 700 m.
authors.affiliation: China Animal Health and Epidemiology Center, Qingdao, China.
authors.forename: H
authors.initials: H
authors.lastname: Liu
authors.affiliation: School of Veterinary Science, the University of Queensland, Gatton, Qld, Australia.|FAO HPAI H5N1 Programme in China, Food and Agriculture Organization of the United Nations, Beijing, China.
authors.forename: X
authors.initials: X
authors.lastname: Zhou
authors.affiliation: China Animal Health and Epidemiology Center, Qingdao, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: China Animal Health and Epidemiology Center, Qingdao, China.
authors.forename: D
authors.initials: D
authors.lastname: Zheng
authors.affiliation: China Animal Health and Epidemiology Center, Qingdao, China.
authors.forename: J
authors.initials: J
authors.lastname: Wang
authors.affiliation: Ningxia Animal Disease Prevention and Control Center, Yinchuan, China.
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.affiliation: Emergency Centre for Trans-boundary Animal Diseases (ECTAD), FAO-RAP, Bangkok, Thailand.
authors.forename: D
authors.initials: D
authors.lastname: Castellan
authors.affiliation: China Animal Health and Epidemiology Center, Qingdao, China.
authors.forename: B
authors.initials: B
authors.lastname: Huang
authors.affiliation: China Animal Health and Epidemiology Center, Qingdao, China.
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
authors.affiliation: School of Veterinary Science, the University of Queensland, Gatton, Qld, Australia.|Child Health Research Centre, the University of Queensland, Herston, Qld, Australia.
authors.forename: R J
authors.initials: RJ
authors.lastname: Soares Magalhães
mesh_terms: D000818:Animals; D002681:China / Q000453:epidemiology; D004196:Disease Outbreaks / Q000662:veterinary; D053124:Influenza A Virus, H5N1 Subtype; D005585:Influenza in Birds / Q000453:epidemiology / Q000821:virology*; D016015:Logistic Models; D015999:Multivariate Analysis; D011200:Poultry / Q000821:virology*; D011201:Poultry Diseases / Q000453:epidemiology / Q000821:virology*; D012189:Retrospective Studies; D012307:Risk Factors
keywords: H5N1 virus; avian influenza; case-control study; outbreak investigation; spatial analysis