title: Outbreaks of H5N1 in poultry in Thailand: the relative role of poultry production types in sustaining transmission and the impact of active surveillance in control.
abstract: H5N1, highly pathogenic avian influenza, continues to pose a public health risk in the countries of southeast Asia where it has become endemic. However, in Thailand, which experienced two of the largest recorded epidemics in 2004-2005, the disease has been successfully reduced to very low levels. We fitted a spatio-temporal model of the spread of infection to outbreak data collected during the second wave of outbreaks to assess the extent to which different poultry types were responsible for propagating infection. Our estimates suggest that the wave of outbreaks would not have been possible without the contribution of backyard flocks to the susceptibility of a sub-district. However, we also estimated that outbreaks involving commercial poultry, a much larger sector in Thailand than in neighbouring countries, were disproportionately infectious, a factor which was also crucial in sustaining the wave. As a result, implemented measures that aim to reduce the role of commercial farms in the spread of infection, such as the drive to bring aspects of the supply chain 'in house', may help to explain the subsequent success in controlling H5N1 in Thailand. We also found that periods of active surveillance substantially improved the rate of outbreak detection.
authors.affiliation: MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Imperial College London, London, UK. patrick.walker@imperial.ac.uk
authors.forename: Patrick
authors.initials: P
authors.lastname: Walker
authors.forename: Simon
authors.initials: S
authors.lastname: Cauchemez
authors.forename: Nienke
authors.initials: N
authors.lastname: Hartemink
authors.forename: Thanawat
authors.initials: T
authors.lastname: Tiensin
authors.forename: Azra C
authors.initials: AC
authors.lastname: Ghani
mesh_terms: D000818:Animals; D004196:Disease Outbreaks; D053124:Influenza A Virus, H5N1 Subtype; D005585:Influenza in Birds / Q000453:epidemiology* / Q000635:transmission*; D008954:Models, Biological; D011200:Poultry; D013785:Thailand / Q000453:epidemiology