CHICKEN HAS never been cheaper. A whole one can be bought for little more than the price of a Starbucks cup of coffee. But the industrial farming methods that make ever-cheaper chicken possible may also have created the lethal strain of bird flu virus, H5N1, that threatens to set off a global pandemic.
According to Earl Brown, a University of Ottawa flu virologist, lethal bird flu is entirely man-made, first evolving in commercially produced poultry in Italy in 1878. The highly pathogenic H5N1 is descended from a strain that first appeared in Scotland in 1959.
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 still easily pass the disease to others, through direct contact or through fecal matter, and lethal strains can evolve. Somehow, the virus that arose in Scotland found its way to China, where, as H5N1, it has been raging for more than a decade.
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. Charoen Pokphand Group, a huge Thai enterprise that owns a large chunk of poultry production throughout Thailand and China as well as in Indonesia, Cambodia, Vietnam and Turkey, exported about 270 million chickens in 2003 alone.
Since then, the C.P. Group, which styles itself as the "Kitchen of the World," has suffered enormous losses from bird flu. According to bird-flu expert Gary Butcher of the University of Florida, the company has made a conscientious effort to clean up. But the damage has been done.
Virulent bird flu has left the factories and moved into the farmyards of the poor, where it has had devastating effects. Poultry may represent a family's greatest wealth. The birds are often not eaten until they die of old age or illness. The cost of the virus to people who have raised birds for months or years is incalculable and the compensation risible: In Thailand, farmers have been offered one-third of their birds' value since the outbreak of bird flu.
Sometimes farmers who don't want to lose their investments illicitly trade their birds across borders. In Nigeria, virus-infected chickens threatened with culling are sold by the poor to even poorer people, who see nothing unusual in eating a sick or dead bird. So the birds -- and the bird flu virus -- slip away to other villages and other countries.
The Southeast Asian country without rampant bird flu is Laos, where 90% of poultry production is still in peasant hands, according to the U.S. Department of Agriculture. About 45 small outbreaks in or near commercial farms from January to March 2004 were quickly stamped out by culling birds from contaminated farms.
Some researchers still blame migratory birds for the relentless spread of the bird flu virus. But Martin Williams, a conservationist and bird expert in Hong Kong, contends that wild birds are more often victims than carriers. Last spring, for instance, about 5,000 wild birds died at Qinghai Lake in western China, probably from exposure to disease at commercial poultry farms in the region, according to Grain. The virus now in Turkey and Nigeria is essentially identical to the Qinghai strain.
Richard Thomas of Birdlife International, a global alliance of conservation organizations, and others dispute the idea that wild birds carried the flu virus from Qinghai to Russia and beyond. They point out that the disease spread from Qinghai to southern Siberia during the summer months when birds do not migrate, and that it moved east to west along railway lines, roads and international boundaries -- not along migratory flyways.
What evidence there is for migratory birds as H5N1 carriers is contained in a study published in the Proceedings of the National Academy of Sciences. Researchers examined 13,115 wild birds and found asymptomatic bird flu in six ducks from China. Analysis showed that these ducks had been exposed earlier to less virulent strains of H5 and thus were partly immunized before they were infected with H5N1. On this slender basis, coupled with the fact that some domestic ducks infected for experimental purposes don't get sick, the study's authors contend that the findings "demonstrate that H5N1 viruses can be transmitted over long distances by migratory birds."