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In a small room adjoining his office in Hanoi, Dr. Nguyen Hong Ha takes a chest X-ray image from a female bird-flu patient and displays it on a light board. Her lungs are covered with scattered clouds that indicate infection. "And this is the next day," he says, slapping another X-ray photo on the board; by now, her lungs are utterly obscured. "This patient died last year," says Ha.
As the director of the National Institute for Tropical Medicine in Hanoi's Bach Mai Hospital, Ha likely has more experience treating human cases of bird flu than anyone. While the rest of the world worries about a future H5N1 pandemic, Vietnamese are suffering right now—40 of the 58 people killed by bird flu since the end of 2003 have died in Vietnam. "During the last eight months, it's been a steady trickle," says Ha. "There's no season for this disease anymore."
H5N1 is unusually lethal. Roughly half of those who have contracted the disease have died, despite the use of artificial respirators and antiviral drugs. That compares with the 10% mortality rate among those who contracted SARS. Ha has watched the virus ravage the lungs of healthy young patients in a matter of days. He says the key to treatment is applying just the right amount of breathing assistance—too much, and an H5N1 patient's weakened lungs can burst. But survival ultimately comes down to "the patient's immune system and the will to fight."
It's a fight that can take everything from survivors but life itself. Before he caught H5N1 this past February, 21-year-old Nguyen Sy Tuan was already slim, carrying just 50 kg on his 1.65-m frame. On his release from Bach Mai Hospital in May, he weighed merely 32 kg. Today, just below his skeletal ribs, his body bears two angry red scars where doctors inserted tubes that pumped fluid out of his lungs; another scar on his throat marks the entry wound for a ventilation tube. Because he passed in and out of consciousness during his 82-day hospital stay, Tuan doesn't remember the tubes piercing his skin, or the local press mistakenly reporting his death. What he held onto was his will to endure. "I remembered that some people had already survived this disease, so I knew I could live," says Tuan, whose younger sister Nguyen Thi Ngoan also beat bird flu. "I always believed in my resistance."
Cases like Tuan's remain rare, because for all its lethality, H5N1 is still an avian virus adapted to killing birds, not people. A flu virus infects a cell by linking its hemagglutinin gene—the H in H5N1—with chemical receptors on the surface of the cell, like a key fitting a lock. Right now H5N1 remains a poor fit for most human cells, and even when it does cause an infection, the virus is concentrated in the lower respiratory system, making it harder to spread to someone else. (Common flu invades the upper respiratory system, and can be spread easily by coughing or sneezing.) But influenza is a master lockpicker, albeit by accident; flu viruses are so mistake-prone in their genetic replication process that they mutate constantly. Flu viruses can also mutate by swapping genes with other strains through reassortment, a process that's believed to have generated the last two pandemic flus. Although the vast majority of mutants prove unfit for survival, there's always a small chance that a new strain could arise that can be transmitted easily from human to human—either through a one-shot reassortment, or through the accumulation of minor mutations. "It's like a frequent flyer program," says Michael T. Osterholm, the head of the Center for Infectious Disease Research and Policy at the University of Minnesota. "Take enough trips and you can go anywhere." And every instance of a person catching H5N1 increases the odds that a deadlier strain will emerge—one with a genetic makeup that is better suited to human hosts. "You're playing Russian roulette every time you have a human infection," says Earl Brown, a virologist at the University of Ottawa.
If H5N1 turns nastier, Ha knows he will not be able to hold back the tide of dead patients. With its eight respirators, only six of which currently work, Bach Mai is as well-equipped as any hospital in the country to deal with a pandemic—which means it's barely equipped at all. Per-capita health expenditure in Vietnam is just $8, enough to buy a single rapid test for influenza. A pandemic, says Ha, "would be a disaster."