Bird Flu Returns: What Past Outbreaks Can Teach Us

The virus probably originates in southern China, but no one knows how it has spread so widely. Transport of infected birds to chicken farms is one theory, but it’s also possible that migratory birds such as ducks and geese are spreading it through their droppings. “Did birds in Hong Kong, which nest in Siberia and North Korea, somehow spread the virus elsewhere?” asks Robert Webster, an expert in animal influenzas at St. Jude Children’s Research Hospital in Memphis, Tenn. “That’s a frightening possibility.” If H5N1 does evolve into a flu that humans can spread, a vaccine could be developed but would take months. “Once you know this virus can spread from human to human, region to region,” says Dr. Yi Guan, a SARS and avian-flu expert at the University of Hong Kong, “it’s already too late.”

For some time, health experts have warned of a worldwide bird-flu pandemic that could kill millions of people and wreck the global economy. “The most serious known health threat facing the world is avian flu,” said WHO director-general Lee Jong-wook earlier this year. And the threat is growing all the time, as nature keeps dropping hints that the links in a chain of events leading to a deadly pandemic continue to be forged. This summer, H5N1 spread west—perhaps in migrating birds—to new territory, including Mongolia, Tibet, Siberia and Kazakhstan. European countries are taking precautions by tightening surveillance of flocks within their borders; in the Netherlands, officials in late August ordered farmers to move the nation’s 90 million poultry indoors to prevent any contact with itinerant fowl. Meanwhile, in Southeast Asia, where at least 58 people have died and 150 million poultry have died or been culled because of avian flu since the end of 2003, the virus is still active; a Jakarta woman died of the disease on Sept. 10. The H5N1 virus has already shown it can be deadly to people who come into direct contact with infected birds or eat uncooked poultry. But bird-to-human transmission is relatively controllable because diseased flocks can be isolated or, usually, eliminated. The sum of all fears is that H5N1 could mutate into a strain with the ability to jump easily from person to person, as ordinary flu does. That could trigger a once-in-a-century catastrophe. How many would die? Nobody knows, or can know.

Indonesia’s chickens are about meat and eggs, of course. But they are also a potentially deadly symbol of changing patterns of food production and consumption. While the H5N1 strain of avian flu has occasionally jumped from birds to people for several years now, the fear is that it will mutate and begin spreading easily from person to person, threatening the lives of millions. So a pandemic is why the world cares about dead chickens in a tiny rural village. Though the rare human bird-flu cases have gotten most of the attention, “the most effective way to prevent a pandemic is to stop the virus in animals,” says Dr. Bernard Vallat, director general of the World Organization for Animal Health (OIE). In other words: save the chickens, save the world.

Why should we spend scarce medical resources swabbing the inside of pigs’ nostrils, looking for viruses? Because new pathogens–including H5N1 bird flu, SARS, even HIV–incubated in animal populations before eventually crossing over to human beings. In the ecology of influenza, pigs are particularly key. They can be infected with avian, swine and human flu viruses, making them virological blenders. While it’s still not clear exactly where the H1N1 virus originated or when it first infected humans, if we had half as clear a picture of the flu viruses circulating in pigs and other animals as we do of human flu viruses, we might have seen H1N1 coming. (When it comes to sniffing out new pathogens, says one epidemiologist, “we’re like a drunk looking for his keys.”) Faster genetic sequencing and the Internet give us the technological means to create an early-warning system. But we need to spend more on animal health and get doctors talking to their veterinarian counterparts. “For too long, the animal side of public health has been neglected,” says Dr. William Karesh, vice president of the Wildlife Conservation Society’s global-health program.