title: Models of highly pathogenic avian influenza epidemics in commercial poultry flocks in Nigeria and Ghana.
abstract: State-scale and premises-scale gravity models for the spread of highly pathogenic avian influenza (H5N1) in Nigeria and Ghana were used to provide a basis for risk maps for future epidemics and to compare and rank plausible culling and vaccination strategies for control. Maximum likelihood methods were used to fit the models to the 2006-2007 outbreaks. The sensitivity and specificity of the state-scale model-generated probabilities that any given state would be involved in an epidemic were each 57 %. The premises-based model indicated that reactive, countrywide vaccination strategies, in which the order in which flocks are vaccinated was strictly determined by known risk factors for infection, were more effective in reducing the final size of the epidemic and the epidemic impact than vaccinating flocks at random or ring vaccination. The model suggests that an introduction of highly pathogenic avian influenza (H5N1) into Ghana had a high chance (84 %) of causing a major outbreak. That this did not happen was most probably a result of the very swift Ghanaian response to news of the first introductions.
authors.affiliation: School of Veterinary Medicine, University of Pennsylvania, New Bolton Center, 382 West Street Road, Kennett Square, PA 19348, USA.
authors.forename: Sky T K
authors.initials: ST
authors.lastname: Pelletier
authors.forename: Chris
authors.initials: C
authors.lastname: Rorres
authors.forename: Peter C
authors.initials: PC
authors.lastname: Macko
authors.forename: Sarah
authors.initials: S
authors.lastname: Peters
authors.forename: Gary
authors.initials: G
authors.lastname: Smith
mesh_terms: D000822:Animal Husbandry; D000818:Animals; D003140:Communicable Disease Control; D003198:Computer Simulation; D004196:Disease Outbreaks / Q000662:veterinary*; D005869:Ghana / Q000453:epidemiology; D053124:Influenza A Virus, H5N1 Subtype / Q000502:physiology; D005585:Influenza in Birds / Q000453:epidemiology* / Q000517:prevention & control / Q000635:transmission; D016013:Likelihood Functions; D008954:Models, Biological; D009549:Nigeria; D011200:Poultry; D011201:Poultry Diseases / Q000453:epidemiology* / Q000517:prevention & control / Q000635:transmission; D012307:Risk Factors