So were health authorities, who initially feared that the Nguyen family cluster meant the H5N1 virus—which usually only spreads from bird to human in isolated cases—might now be moving from person to person. Since the disease first began jumping from birds to people in 1997, scientists have been worried that the lethal virus could mutate to gain the ability to transmit from one person to another as easily as a normal human-flu virus. That would open the door for a global influenza pandemic that could kill millions.
But epidemiological investigations have shown it may be equally probable that the brothers were infected by their raw-duck-blood porridge as by each other. "It's too early to tell," says Hans Troedsson, the World Health Organization's (WHO) Hanoi representative. Even if there was person-to-person transmission within the family, it hasn't spread farther, as a pandemic-causing virus likely would. (A recent New England Journal of Medicine article confirmed that such limited human-to-human transmissions occurred last September in Thailand.) But the threat of a pandemic hasn't diminished: as of last Friday, Vietnam has reported 15 human cases of bird flu since mid-December, 11 of whom have already died. The virus has spread to poultry populations in almost half of the country's 64 provinces. Most worrisome of all, the increased poultry sales and mass travel that mark the coming Tet Lunar New Year festival (beginning Feb. 9) are the perfect ingredients for an explosive rise in infections—and every infection gives the H5N1 virus the opportunity to further adapt to humans. "If something is going to cook, Tet is when it's going to happen," says Dr. Robert Webster, an avian-flu expert at the St. Jude Children's Research Hospital in Memphis.
The good news is that Vietnamese authorities, who badly mismanaged past outbreaks, are doing far more to ensure that the Year of the Rooster doesn't become the Year of Bird Flu. The southern metropolis of Ho Chi Minh City has closed its unhygienic wet markets, which sold live chickens and ducks, forcing all incoming poultry to be killed at slaughterhouses. Market monitors, backed by riot police, are manning checkpoints on major highways to ensure that all incoming poultry have "passports" proving that they've been inspected by government veterinarians for avian flu. Since December, 800,000 birds have been culled in the ongoing effort to eradicate the outbreak; 40 million of Vietnam's 258 million total poultry population have been culled since the disease first emerged in late 2003. "They're definitely responding much better than this time last year," says Dr. Hitoshi Oshitani, an avian-flu expert based at the WHO's Western Pacific regional office.
These efforts haven't come cheap: the Ministry of Agricultural and Rural Development estimates the economic loss of all that poultry at just under 0.5% of GDP, or $195 million. Nguyen Vau Be and his family in rural Long An province raised 100 ducks to pay for their holiday celebrations and food this year, but when the birds became sick recently, they were forced to kill them. "There's no Tet for us this year," says wife Truong Thi Dua, watching as the live ducks are tossed onto a large bonfire. The family is being compensated with a total of $32 for their culled birds, less than they borrowed to buy them as ducklings last year. "Now we have nothing, not even enough money to buy ingredients for one banh chung [bean paste and pork] cake," says Truong. Village chief Huynh Van Tiep, who is overseeing the cull, says the Nguyens aren't alone. "Our whole village depended on poultry," he says. "I feel terrible asking people to kill their livelihood, but public health is more important."
Vietnam's traditional poultry practices are dangerous because dense populations of people and birds mingle at virtually every step of production, from chick to phó pot. With the virus embedded in the local duck and chicken population, repeated human-bird contact means "it's inevitable you'll get human infection," says Webster. Vietnam is trying to halt such infections by modernizing its poultry industry, limiting human-bird contact, but that won't be easy. More than 80% of its poultry producers are small-scale farmers who raise a few dozen birds to eat or sell—and few keep their flocks in cages or enclosures. "Rural Vietnam is one huge free-range farm," says Anton Rychener, head of the Hanoi office of the U.N. Food and Agriculture Organization. Although Ho Chi Minh City has shut down its once ubiquitous wet markets, it still isn't hard to find a live chicken for sale there. Two blocks from Cho Lon market, where rows of empty cages once housed squawking chickens, a vegetable vendor offers to locate live poultry for a finder's fee of about 60¢. She leads her customers to a back alley where a woman in a baseball cap opens several plastic bags, revealing four live chickens. For $2.50, the woman—who refuses to give her name—grabs a bird and slits its throat, letting the blood drain onto a tray. "It's only sick chickens that are dangerous," she says. "This one is alive, so it's O.K." (Not true: infected birds can sometimes spread the disease before showing symptoms.)
Given enough time, Vietnam should be able to tighten control over its poultry trade. The trouble is, bird flu may not wait that long. The disease is already endemic in much of Asia, and a recent WHO report showed that the H5N1 virus has become progressively hardier and more lethal, with a human mortality rate of 75%. Dr. Jeremy Farrar, director of the Oxford University Clinical Research Unit at the Hospital for Tropical Diseases in Ho Chi Minh City, says he's shocked by the virulence of avian flu in the patients he has helped treat: "I've never experienced anything like it in terms of its destructive power. It is staggering in terms of how much lung tissue is destroyed." Nguyen Thanh Hung, one of the few to survive avian flu, says the disease is pure misery. "I felt like my head was about to explode. My heart was pounding like it would come out of my chest, and I couldn't control my muscles."
The viciousness and intractability of bird flu are forcing the world to begin preparing for a pandemic. At the WHO's 32-nation executive board meeting last week, health officials debated plans to strengthen disease surveillance, stockpile antiviral drugs like Tamiflu, and boost research on a human vaccine that will soon go into clinical trials. In Thailand, where 12 people have died of the disease since the beginning of 2004, the government last week launched a $117 million fund to fight avian flu over the next three years, with an 800,000-strong team of volunteers. Experts say that kind of initiative is needed from every country. "We live in a highly integrated world," says Dr. William Aldis, head of the WHO's Bangkok office. "The worst country in the world as far as surveillance and control methods sets the level of risk for all of us." That means what happens while Vietnam celebrates the Year of the Rooster could have implications for everyone.