title: Influenza A H5N1 and H7N9 in China: A spatial risk analysis.
abstract: BACKGROUND
  Zoonotic avian influenza poses a major risk to China, and other parts of the world. H5N1 has remained endemic in China and globally for nearly two decades, and in 2013, a novel zoonotic influenza A subtype H7N9 emerged in China. This study aimed to improve upon our current understanding of the spreading mechanisms of H7N9 and H5N1 by generating spatial risk profiles for each of the two virus subtypes across mainland China.
  
  
  RESULTS
  In this study, we (i) developed a refined data set of H5N1 and H7N9 locations with consideration of animal/animal environment case data, as well as spatial accuracy and precision; (ii) used this data set along with environmental variables to build species distribution models (SDMs) for each virus subtype in high resolution spatial units of 1km2 cells using Maxent; (iii) developed a risk modelling framework which integrated the results from the SDMs with human and chicken population variables, which was done to quantify the risk of zoonotic transmission; and (iv) identified areas at high risk of H5N1 and H7N9 transmission. We produced high performing SDMs (6 of 8 models with AUC > 0.9) for both H5N1 and H7N9. In all our SDMs, H7N9 consistently showed higher AUC results compared to H5N1, suggesting H7N9 suitability could be better explained by environmental variables. For both subtypes, high risk areas were primarily located in south-eastern China, with H5N1 distributions found to be more diffuse and extending more inland compared to H7N9.
  
  
  CONCLUSIONS
  We provide projections of our risk models to public health policy makers so that specific high risk areas can be targeted for control measures. We recommend comparing H5N1 and H7N9 prevalence rates and survivability in the natural environment to better understand the role of animal and environmental transmission in human infections.
authors.affiliation: School of Public Health and Community Medicine, University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Chau Minh
authors.identifier: http://orcid.org/0000-0001-9046-5810
authors.initials: CM
authors.lastname: Bui
authors.affiliation: School of Civil and Environmental Engineering, University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Lauren
authors.initials: L
authors.lastname: Gardner
authors.affiliation: School of Public Health and Community Medicine, University of New South Wales, Sydney, New South Wales, Australia.|College of Public Service & Community Solutions, Arizona State University, Phoenix, Arizona, United States of America.
authors.forename: Raina
authors.initials: R
authors.lastname: MacIntyre
authors.affiliation: Departments of Philosophy and Integrative Biology, University of Texas, Austin, Texas, United States of America.
authors.forename: Sahotra
authors.initials: S
authors.lastname: Sarkar
mesh_terms: D000818:Animals; D001717:Birds; D002681:China / Q000453:epidemiology; D004196:Disease Outbreaks; D019353:Endemic Diseases; D006801:Humans; D053124:Influenza A Virus, H5N1 Subtype; D064766:Influenza A Virus, H7N9 Subtype; D005585:Influenza in Birds / Q000453:epidemiology / Q000628:therapy / Q000821:virology; D007251:Influenza, Human / Q000453:epidemiology* / Q000635:transmission / Q000821:virology*; D008954:Models, Biological; D012307:Risk Factors; D062206:Spatial Analysis; D015047:Zoonoses / Q000453:epidemiology / Q000635:transmission / Q000821:virology