Wild-bird flu depends on mobile hosts to spread. If flu strains kill their hosts in the wild, the lethal versions will vanish. This is why evolution pushes wild-bird strains toward mildness.But if it’s hard for a lethal virus to get a foothold in the wild, how have migratory birds been spreading the deadly H5N1 bird flu? Could be that they’re not. See "Evolutionary no man’s land — pandemic flu and the underreported meme." Orent is among those who see modern factory farming, especially the way it’s practiced in Asia these days, as an evolutionary breeding ground for lethal viruses.
People have been living with backyard flocks of poultry since the dawn of civilization. But it wasn't until poultry production became modernized, and birds were raised in much larger numbers and concentrations, that a virulent bird flu evolved. When birds are packed close together, any brakes on virulence are off. Birds struck with a fatal illness can easily pass the disease to others, through direct contact or through fecal matter, and lethal strains can evolve.Perhaps because it’s easier to blame wild birds than to take a closer look at the practices of modern agribusiness, many experts were skeptical. But according to the New York Times, evidence is mounting that there’s more to the story than the presumed ability of migratory birds to pass this virus over vast distances.
Industrial poultry-raising moved from the West to Asia in the last few decades and has begun to supplant backyard flocks there. According to a recent report by Grain, an international nongovernmental organization, chicken production in Southeast Asia has jumped eightfold in 30 years to about 2.7 million tons. The Chinese annually produce about 10 million tons of chickens. Some of China's factory farms raise 5 million birds at a time.
Although many countries attribute the spread of (A)H5N1 to migratory fowl, many ornithologists say the evidence often points to smuggling.The good news is that modern agriculture keeps chicken prices low, but maybe that's also the bad news. The way Mother Nature balances her books, we may be paying a very steep price for cheap chicken.
"We believe it is spread by both bird migration and trade, but that trade, particularly illegal trade, is more important," said Wade Hagemeijer, a bird flu expert at the Netherlands-based Wetlands International, which has been studying the role of migrating birds.
Although bird flu has now been detected on many farms in several African nations, there have been only a handful of reports of infections in wild birds on the continent, supporting the notion that trade is most important there.
"We're been looking for it in wild birds for the last two months and it is surprising that we've come up with zero," Dr. Lubroth said.
The effect of smuggling can sometimes be direct, when sick birds are smuggled onto farms. The virus strain found on the farms involved in Nigeria's first outbreak, in northern Kano State, closely matched those found on Chinese farms, Mr. Hagemeijer said.