According to the Centers for Disease Control and Prevention (CDC), influenza has been a common communicable disease in birds for centuries (see "Connecting the Dots," cover story, November/December 2004). Most strains are confined only to birds and are generally non-lethal, much like human influenza viruses. Recently though, there have been questions raised over the H5N1 strain of avian influenza that has been crossing over into human beings in Southeast Asia. The CDC claims that the three main strains of human influenza probably originally came from birds, yet this one in particular is different, since it is highly contagious and very deadly.
Simon Hable of the World Wildlife Fund says that the western hemisphere has yet to see a real threat from avian flu, and he says the exotic bird trade, mainly centered in Europe, has been tightened. Still, he worries about a potential increase in illegal bird trading due to increased restrictions. He adds, "It only takes one contact with one human before this could take off."