NEW YORK -- Scientists at the Consortium for Conservation Medicine, Royal Society for the Protection of Birds and Smithsonian Institution's National Zoo report H5N1 avian influenza is most likely to be introduced to countries in the Western Hemisphere through infected poultry trade.

Following initial outbreaks of H5N1 avian influenza in Hong Kong, scientists and government officials worldwide have debated exactly how the virus was being spread and what could be done to stop it.



Marm Kilpatrick, senior research scientist with CCM, led the team in its efforts to predict the most likely method of introduction to the U.S. Kilpatrick and colleagues predict that bird flu will most likely be introduced to countries in the Western Hemisphere through infected poultry trade rather than from migrating birds from eastern Siberia, as previously thought. The subsequent movement of infected migrating birds from countries south of the U.S. would be a likely pathway for H5N1 avian influenza to reach the USA.



Avian influenza has reached more than 50 countries, and millions of chickens have been either infected and/or culled to prevent its spread to other poultry farms. Estimated financial losses are in the tens of billions of dollars. In addition, 258 people have been infected and 153 human deaths have occurred, with most cases in Vietnam, Indonesia, Thailand, and China.



This new research set out to identify the pathways for individual H5N1 introductions as the virus spread through Asia, Europe and Africa. The predictive modeling approach used offers substantial promise for understanding past introductions, the pathway for new introductions, and ways to prevent future spread of the deadly virus.



The researchers analyzed the risk of introduction by three different pathways: poultry, wild bird trade, and movement of migratory birds.



"To determine the pathway of introduction we gathered global data on country-to-country trade in poultry and wild birds and mapped out the migratory routes of every species of duck, goose, or swan. We then compared our analyses based on these data to the relationships between virus isolates from the different countries," said Kilpatrick.



Robert Fleischer, a Smithsonian Institution scientist, noted, "The rate of genetic change of the virus is extremely fast, which means we can use genetic analysis to trace the geographic and evolutionary pathways the virus has taken."



The findings showed that migratory bird movements were likely responsible for three introductions in Asia, 20 in Europe, and three in Africa. David Gibbons, Head of Conservation Science with UK's Royal Society for the Protection of Birds, said, "Much of the spread of H5N1 around Europe followed an unusually cold period of weather in central and eastern Europe in January and February 2006, with wild birds moving west through Europe in search of more clement conditions, some carrying H5N1 with them. As part of the UK government's AI surveillance strategy, RSPB staff will be looking for sick or dead ducks, geese and swans this winter."



Peter Marra, an avian ecologist with the Smithsonian's Migratory Bird Center at the National Zoo commented, "In almost all cases in which we have detected H5N1 in wild birds, it has been found in dead birds. It's critical that dead bird surveillance mechanisms be developed for early detection of H5N1 and other diseases."



In comparison, poultry trade was responsible for two introductions to countries in Africa and nine important introductions in Asia where the disease is still infecting humans and poultry. "The synergistic combination of poultry trade and migratory bird movements spread H5N1 much further than it would have gone by either of these pathways alone," said Kilpatrick.



Peter Daszak, Executive Director of CCM stated, "This study shows how trade between continents opens the door for pathogens to move effortlessly along those routes. The study of Conservation Medicine strives to understand how human activities drive disease spread and proposes critical action steps on preventing future pandemics."



Donald Burke, Dean of the University of Pittsburgh Graduate School of Public Health, and an advisor to the group, said, "This report shows how we can move beyond the conventional surveillance and response mode to one of prediction and prevention."



Mary Pearl, President of Wildlife Trust and co-founder of CCM noted, "Fully three-quarters of new diseases have an animal origin. By researching the links among wildlife, livestock, and humans, we can preempt the movement of many new disease-causing agents to people."



The Consortium for Conservation Medicine is a coalition of six scientific organizations that enables scientists from multiple disciplines to collaborate on key issues of human, animal and environmental health and conservation. The CCM is a think-tank for the origin, prediction, and prevention of emerging diseases.

SOURCE: The Consortium for Conservation Medicine via Business Wire.