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Cases of avian flu in migratory birds that fly along what is known as the East Asia/Australian Flyway (a complicated web of flight paths rather than a single route) have generated substantial concern in the health community. Yet experts are not uniform in their views on the role that migratory waterfowl might play in spreading H5N1 to other species. One of the greatest fears is that infected migratory birds could pass avian flu to humans, especially through their droppings. Migratory birds travel tremendous distances, and countless humans and other mammals could be exposed to their fecal matter without the birds ever setting foot on the ground. Skeptics note that, to date, nearly all human victims of H5N1 have had steady and substantial exposure to infected birds and by definition, migratory birds do not have such human contact. Others question whether any infected birds could survive long enough to continue their migration. They note, for example, that 1,500 migratory birds testing positive for H5N1 were recently found dead at Qinghai Lake in China. However, to date, none of their surviving peers have been known to carry the virus, and no human infections have been reported in connection with this cluster.
Even if migratory birds do not live long enough to spread the virus today, it could all change in the future. Chickens and ducks can now live substantially longer with H5N1 than they could when the strain was first identified, with some ducks reportedly remaining asymptomatic, suggesting that migratory birds might eventually be able to travel longer distances with the virus. And even if migratory birds do not directly infect people, spreading the virus to domestic fowl around the world could have disastrous results. The World Health Organization, the United Nations Food and Agriculture Organization, and other leading international organizations have cited migratory birds as a significant source of concern. Yet they have also noted that attempting to control avian migration is not a realistic option.
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Next: The Human Factor
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Sources: Asian Development Bank; Australasian Wader Study Group; World Organization for Animal Health; World Health Organization; Food and Agriculture Organization of the United Nations; Recombinomics, Inc.; Wildlife Conservation Society; NEW SCIENTIST; ProMed
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Intro - Read a briefing on the dangers posed by avian influeza and the challenges nations must overcome in order to fight against it.
Photo Essay - Learn more about influenza and science's sruggle against it.
Filmmaker Notes - Go behind the scenes with producer Micah Fink.
Interactive Map - Get the facts about the AIDS pandemic in sub-Saharan Africa.
Interactive Challenge - Test your knowledge of AIDS in Africa.
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