Evidence for the Convergence Model: The Emergence of Highly Pathogenic Avian Influenza (H5N1) in Viet Nam

Abstract

Building on a series of ground breaking reviews that first defined and drew attention to emerging infectious diseases (EID), the ‘convergence model’ was proposed to explain the multifactorial causality of disease emergence. The model broadly hypothesizes disease emergence is driven by the co-incidence of genetic, physical environmental, ecological, and social factors. We developed and tested a model of the emergence of highly pathogenic avian influenza (HPAI) H5N1 based on suspected convergence factors that are mainly associated with land-use change. Building on previous geospatial statistical studies that identified natural and human risk factors associated with urbanization, we added new factors to test whether causal mechanisms and pathogenic landscapes could be more specifically identified. Our findings suggest that urbanization spatially combines risk factors to produce particular types of peri-urban landscapes with significantly higher HPAI H5N1 emergence risk. The work highlights that peri-urban areas of Viet Nam have higher levels of chicken densities, duck and geese flock size diversities, and fraction of land under rice or aquaculture than rural and urban areas. We also found that land-use diversity, a surrogate measure for potential mixing of host populations and other factors that likely influence viral transmission, significantly improves the model’s predictability. Similarly, landscapes where intensive and extensive forms of poultry production overlap were found at greater risk. These results support the convergence hypothesis in general and demonstrate the potential to improve EID prevention and control by combing geospatial monitoring of these factors along with pathogen surveillance programs.

Emerging infectious disease, the household built environment characteristics, and urban planning: Evidence on avian influenza in Vietnam

“…Finucane, Nghiem, et al, 2014) or quantitatively (e.g. Saksena et al, 2015); since one of our goals is to provide precise policy recommendations at a national level, we have used the latter approach. The data discussed here were made possible by National Science Foundation (grant # 0909410) and facilitated through close collaboration with Vietnam's Ha Noi University of Agriculture.…”

Household cooking fuel use in rural and peri-urban Viet Nam: A multilevel longitudinal analysis of supply side factors

“…Viet Nam's GIS commune level shapefile was made available to us through another project along with other common geographical layers (roads, rivers, etc.) (Saksena, Fox, Epprecht, et al 2015).…”

“…By extension of this logic, we recommend that even future studies of urban fuel use should aim to differentiate between modern urban places and the less modern urban places (Saksena, Fox, Spencer, et al 2014). For a few health outcomes previous studies have shown that the rural-urban dichotomy paradigm is either not valid or is not a refined way of examining the true effects of urbanization and modernization (Allender, Foster, Hutchinson, et al 2008;Allender, Wickramasinghe, Goldacre, et al 2011;Allender, Lacey, Webster, et al 2010;Coogan, White, Evans, et al 2011;Dahly and Adair 2007;Jones-Smith and Popkin 2010;McDade and Adair 2001;Novak, Allender, Scarborough, et al 2012;Riha, Karabarinde, Ssenyomo, et al 2014;Saksena, Fox, Epprecht, et al 2015). We believe then that for all the health effects too associated with the use of cooking fuels the same would hold.…”

Effect of biosecurity measures and early detection systems, mitigation measures and surveillance strategies on the spread of HPAI and LPAI between farms

“…The European Food Safety Authority reserves its rights, view and position as regards the issues addressed and the conclusions reached in the present document, without prejudice to the rights of the authors. (Rabl et al, 2009) Language (Ramakrishnan et al, 2009) Not relevant outcomes (Ramey et al, 2014) Not relevant outcomes (Ramis et al, 2014) Not relevant outcomes (Rauw et al, 2012) Not relevant outcomes (Rauw et al, 2011) Not relevant outcomes (Rawdon et al, 2010 (Sakoda et al, 2012) Territory (Saksena et al, 2015) Territory (Salman, 2009) Not relevant outcomes (Sansyzbay et al, 2013) Study population (Sarikaya and Erbaydar, 2007) Study population (Sartore et al, 2010) Not relevant outcomes (Schmitz et al, 2013) Not relevant outcomes (Schroeer et al, 2009) Not relevant outcomes (Schroeer et al, 2011) Not relevant outcomes (Schultsz et al, 2009) Study population (Schweiger and Buda, 2013) Language Study population (Senne, 2010) Territory The present document has been produced and adopted by the bodies identified above as authors. This task has been carried out exclusively by the authors in the context of a contract between the European Food Safety Authority and the authors, awarded following a tender procedure.…”