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Environmental Stresses Increase Risk of Avian Flu Outbreak


New evidence suggests that the avian flu virus -- now confirmed in 45 countries on three continents in Asia, Europe and Africa -- might spread more quickly in ecosystems damaged by human activities. That's the finding of a report commissioned by the United Nations Environment Program and the World Health Organization.

David Rapport, honorary professor of medicine and dentistry at the University of Western Ontario is the report's lead author. He says unhealthy ecosystems, stressed by human activities, are hotbeds for the increase in disease prevalence in plants and animals. "These diseases may, in the case of H5N1, transfer across species lines into humans," he says.

Two hundred million infected or at-risk birds have been killed since the first H5N1 outbreak in 2003. Half of the 192 people known to have been infected by diseased poultry have died. Right now, the avian flu strain can't be passed from human to human, but health officials fear a natural mutation might enable it to do so.

Rapport says loss of habitat is forcing wild birds known to carry the virus into closer contact with domestic fowl. "If you reduce the wetland habitat, birds are adaptive. They are going to look for other habitats on which to feed, and breed and take refuge in migratory flights," he says. "What we find now is the secondary habitat that is available is in farming areas, the very areas where the high production poultry operations are going on."

Rapport says even when birds are kept in cages, their waste can spread and breed infection. "The virus can live in those waste products, can live in feed products, can live in water, can be an effective way to transfer [the virus] from poultry to wild birds."

He says control strategies such as livestock culls, quarantines, and vaccines are likely to be quick fixes that offer only short-term benefits. In the long run, the UN report calls for re-examining how poultry is raised, eliminating farms under migratory flyways and increasing efforts to restore wetlands.

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