Few countries remain today where H5N1 avian influenza would persist should it be introduced
19 August 2010 - The highly pathogenic avian influenza H5N1 virus (H5N1 HPAI) that swept through Southeast Asia in 2004 has spread across Eurasia and into Africa. To date, a total of 62 countries or territories have reported cases of this disease. Its persistence in some countries continues to disrupt poultry production, impairs smallholder livelihoods, and raises the risk of a strain adapted to human-to-human transmission to emerge.
Previous studies have identified a limited number of key agro-ecological risk factors such as free-grazing domestic ducks and floodplain rice agriculture that appear to be associated with H5N1 HPAI persistence in poultry in Southeast Asia. However, not much is known of such factors in countries with different agro-ecological conditions.
Given that no study has ever investigated the impact of agro-ecological conditions on H5N1 HPAI epidemiology at the global scale, a multidisciplinary research team explored the patterns of H5N1 HPAI persistence worldwide, on a country basis, and for China, Indonesia and India, including the individual provinces that reported H5N1 HPAI presence from 2004 to 2008.
This research shows that a combination of six variables discriminates the areas from where H5N1 HPAI in humans has been reported and/or where the available data suggested persistent virus circulation in poultry. These are: (1) agricultural population density, (2) duck density, (3) duck by chicken density, (4) chicken density, (5) the product of agricultural population density and chicken output/input ratio, and (6) purchasing power per capita.
Identification of these key variables followed rigorous statistical analysis of a set of 14 agricultural, environmental, climatic, and socio-economic factors. Further analysis identified five agro-ecological niches representing varying degrees of disease persistence. This information was used in turn to map H5N1 HPAI risk aroung the globe.
The practical implication of these findings is that only a few countries remain today where H5N1 HPAI would likely persist should it be introduced. In addition, it is now much better understood why the fight against this disease is so hard in the countries that remain infected.
More about this study and other details in relation to this topic can be found in “Persistence of Highly Pathogenic Avian Influenza H5N1 Virus Defined by Agro-Ecological Niche” published in EcoHealth journal, June 2010.
The Food and Agriculture Organization of the United Nations (FAO) supports this type of study in order to clarify feasible and viable options to address high-impact transboundary diseases that are emerging and re-emerging around the world.