Desolate but beautiful, tucked in a northwest corner of China so distant from populated areas that it lies near the spot where Beijing developed its first atomic bomb, Bird Island could be the last place on Earth. But for migratory birds, the island—actually a small peninsula protruding into Qinghai Lake, China's largest saltwater lake—is the avian equivalent of a busy international airport. Each year in the late spring and summer, hundreds of thousands of wild birds of almost 200 different species land here to lay eggs and hatch their young, before departing for wintering grounds that range from Europe to South Asia. On May 4, Li Yinghua, a ranger at the Qinghai Nature Reserve's Bird Island Station, was making his daily rounds near an area popular with bar-headed geese when he spotted something he'd never seen in his two decades at the reserve. "One of the geese had wandered away from the group," he recalls. "It was walking so strangely, wobbling from side to side as if it were drunk." His voice drops to a whisper. "This goose seemed to be shivering." Li called his superiors who took the animal away for tests. He heard that it died soon after.
Over the next six weeks, thousands of other birds, chiefly bar-headed geese, would perish in the same way. In Hong Kong, animal virologist Guan Yi heard about Qinghai and immediately guessed that he knew the cause: H5N1, a deadly avian-flu virus that has ravaged Southeast Asia's poultry flocks and infected over 100 people since the end of 2003. Although the Chinese government initially rebuffed requests by the Geneva-based World Health Organization (WHO) to visit the site of the Qinghai outbreak—they wouldn't be given clearance until the end of June—Guan circumvented the red tape, using his network of mainland contacts to gather nearly 100 samples from dead birds. The results, which he and his team published on July 7 in the journal Nature, confirmed his suspicion: wild birds, generally thought to be immune to the effects of H5N1, were succumbing to the virus. That was important news. If H5N1 became established among migratory species, it would raise the risk that the virus could be spread across oceans and continents. Understanding just how the viral transmission belt operates "is urgent work for the entire world," Guan told Time recently, speaking in his office at the University of Hong Kong (HKU). "The virus could go to Europe, and from there to India. These questions are critical not just for science, but for humankind."
If that sounds like an alarmist's hype, it's not. 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. But in the great flu pandemic at the end of World War I, up to 100 million lost their lives (see sidebar).
Another global flu pandemic that horrific is not inevitable. "The scientists at the WHO and elsewhere who have been beating the drum about the coming flu pandemic are overstating the evidence," says Paul Ewald, an evolutionary biologist at the University of Louisville. Standards of public health in much of the world are far better than they were in 1918. There is better understanding than ever before of how a disease propagates, and how it kills. New antiviral drugs are available—though there are not enough to go around in the event of a worldwide outbreak—and H5N1 vaccines are being developed by French drugmaker Sanofi-Aventis and U.S. biotechnology company Chiron. In the wake of Hurricane Katrina, which demonstrated the high cost of complacency, the world is beginning to heed WHO warnings—last week, U.S. President George W. Bush proposed an international partnership to fight the disease, and rich countries including Britain, France and South Korea have stepped up orders for antiviral drugs that could help to protect their citizens in an outbreak. But none of these factors, alone or together, are enough to let the world sleep easy. As Time reporters worked on this story—talking to a virologist hunting for genetic clues in the muddy backyard chicken farms of Asia, a doctor in Vietnam who attends some of those who have already been infected by H5N1, and an epidemiologist in the U.S. who tracks the movement of the virus around the globe—they were left with one abiding impression. Though we have the ability to prevent or mitigate a flu pandemic, those in the frontline of the battle against H5N1 are preparing for the worst. This is their story.