The landscape epidemiology of seasonal clustering of highly pathogenic avian influenza (H5N1)

Lead Author Philippe, Amstislavski
Institution Contact Department of Health Sciences University of Alaska - Anchorage 3211 Providence Drive Anchorage, AK 99508
Co-Authors Michael G. Walsh, Department of Epidemiology and Biostatistics, School of Public Health, State University of New York, USA, Andrea Greene Department of Epidemiology and Biostatistics, School of Public Health , State University of New York, USA, M.A. Haseeb, Departments of Cell Biology, Pathology and Medicine, College of Medicine, State University of New York, USA, Douglas Causey, Department of Biological Sciences, University of Alaska -- Anchorage, USA
Theme Theme 4: Building Long-term Human Capacity
Session Name 4.4 Circumpolar Health and Well-Being
Presentation Type Poster
Abstract text Background: A total of 694 human infections with Highly pathogenic avian influenza subtype H5N1 (death rate 58%) were recorded during 2003–2014. H5N1 has also contributed to substantial economic loss each year since 1997. While the distribution of domestic bird H5N1 outbreaks across Europe, North America, Africa, and Asia is extensive, those features of the landscape conferring greatest risk remain uncertain. Furthermore, the extent to which influential landscape features may vary by season has been inadequately described. Relationship of the proximity of domestic birds to wild birds' flyways and to surface water, which would be expected to facilitate viral transmission between domestic and wild birds is also poorly understood.

Methods: The current investigation used World Organization for Animal Health surveillance data to 1) delineate areas at greatest risk for H5N1 epizootics among domestic poultry, 2) identify those abiotic and biotic features of the landscape associated with outbreak risk, and 3) examine patterns of epizootic clustering by season. Inhomogeneous point process models were used to predict the intensity of H5N1 outbreaks and describe the dependencies between them.

Results: During October through March, decreasing precipitation, increasing isothermality, and the presence of H5N1 in wild birds were significantly associated with increased risk of domestic H5N1 epizootics. Conversely, increasing precipitation and decreasing isothermality were associated with increased risk during April through September. Increasing temperature during the coldest quarter, domestic poultry density, and proximity to surface water were associated with increased risk of domestic outbreaks throughout the year. Dependencies between outbreaks appeared to vary by season, with substantial clustering at small and large scale identified during October through March even after accounting for inhomogeneity due to landscape factors. In contrast, during April to September, H5N1 outbreaks exhibited no clustering at small scale once accounting for landscape factors.

Conclusions: This investigation has identified seasonal differences in risk and clustering patterns of H5N1 outbreaks in domestic poultry, and may suggest strategies in high risk areas with features amenable to intervention such as controlling domestic bird movement in areas of high poultry density or preventing contact between poultry and wild birds and/or surface water features.