Martin W
Those of us who have been studying avian influenza and other bird diseases for decades, when few people beside pet owners and the poultry industry cared, are dismayed that voices of reason are being drowned out with regard to the role played by wild birds in the spread of the H5N1 virus. This past week alone, both the United Nations and the Office of Homeland Security implicated migratory birds as the most likely carriers of H5N1 to American shores, while cable news scrambled to get bird migration maps. Migratory fowl could, of course, bring H5N1 here on the wing. But there is an equal, if not greater, chance that H5N1 will fly to North America on an airplane transporting poultry legally or otherwise.

Recently a shipment of chicken feet was smuggled into the United States from Thailand, arriving in Connecticut marked "jellyfish." Luckily, our trade surveillance system worked and the chicken parts were confiscated. Over the last 30 years we have learned a tremendous amount about how avian influenza spreads. In nature, avian influenza viruses live innocuously in many types of wild birds and cause only mild effects, sometimes none at all, similar to many bacteria and viruses that live in humans.

This is not to say that the virus can't be carried by, and kill, wild birds, because it can. Yet the spread of H5N1 did not result from the activities of wild birds, but from a very human activity – trade. We know that international trade in wild or exotic birds, both legal and illegal, has helped moved H5N1 around the world. However, the virus has likely gotten its biggest boost through the trade, both legal and illegal, in poultry. As part of a multi-billion dollar industry, poultry markets and farms span the globe. The conditions of these facilities vary greatly; some are plagued by highly unsanitary conditions and close bird-to-bird contact. This environment provides the ideal setting for deadly strains of the avian flu virus to develop.

Moving these infected poultry and poultry products as well as contaminated fecal matter on trucks, boots or in cages results in the further spread of avian flu. The current focus on the role of migratory birds in the spread of H5N1 has shifted discussion away from this trade. … (Robert Cook is chief veterinarian and vice president and William B. Karesh is director of the Field Veterinary Program at the Wildlife Conservation Society, Bronx Zoo, New York.)

Don't blame the wild birds