New Research Predicts Pathways Of Past And Future Spread Of H5N1 Avian Influenza
14 Dec, 2006 01:01 am
The spread of highly pathogenic H5N1 avian influenza into Asia, Europe and Africa has resulted in enormous impacts on the poultry industry and presents an important threat to human health. Avian influenza has reached more than 50 countries, and millions of chickens have been either infected and/or culled to prevent the spread of the virus to other poultry farms. Estimated financial losses are in the tens of billions of dollars from its spread. In addition, 258 people have been infected and 153 human deaths have occurred, with most cases in Vietnam, Indonesia, Thailand, and China. The pathways by which the virus has and will spread between countries have been debated extensively, but have yet to be analyzed comprehensively and quantitatively.
Their predictive model suggested that H5N1 avian influenza was more likely to be introduced to countries in the Western Hemisphere through infected poultry trade rather than from migrating birds from eastern Siberia, as previously thought. This was due to large quantities (greater than 2 million birds per year) of live poultry imported from countries in Europe that had had outbreaks of bird flu. These imports were primarily into Canada, Mexico, Brazil, the USA, Venezuela and Columbia. Quarantine procedures in the USA and Canada (30 days plus testing for bird flu) make introduction of bird flu into these countries through infected poultry less likely than into other countries that canít afford the high costs of these practices.
If infected poultry were imported into Central or South America, this would devastate the poultry industry in these countries and may also result in the spill over of the virus into migratory birds which interact with the free range poultry in many countries. The subsequent movement of infected migrating birds from countries south of the U.S. would then be a likely pathway for H5N1 avian influenza to reach the USA. These results highlight the potential synergism between trade and wild animal movement in the emergence and pandemic spread of pathogens, demonstrating the value of predictive models for disease control.
This research offered a number of policy recommendations. First, all countries in the Americas should focus their attention on careful importation of poultry into their own countries, as well as towards developing regional quarantine procedures to protect poultry in the entire region from becoming infected with the virus. Second, the USA and Canada should conduct surveillance and plan for the possibility that the virus might be carried by birds migrating from the south rather than primarily through Alaska. Third, and more broadly, countries in the region should consider the benefits of more local trade agreements that would reduce the risk of importing bird flu and other pathogens from other regions of the world.
 Kilpatrick, A. Marm et al. Predicting the global spread of H5N1 avian influenza. PNAS 19 December 2006. www.pnas.org/cgi/doi/10.1073/pnas.0609227103