“Even though the big flyway maps look like they overlap, the birds themselves don’t,” says Dr. William Karesh, director of the field veterinary program of the Wildlife Conservation Society. Gene studies of avian-flu strains from the past 30 years seem to confirm that, with no evident commingling among the viruses. “The birds of the New World and the birds of the Old World don’t share their viruses,” Karesh says. “That doesn’t mean it’s impossible. That would be irresponsible. But it doesn’t happen normally.”
In any event, most commercial chicken houses (where the birds spend their entire lives indoors) have no contact with migratory birds. Even free-range chickens are generally not clucking all over hither and yon and so can easily be brought indoors if need be. That still leaves the exotic-pet market (legal and illegal) and the illegal importation of poultry products. (Full Article)