Even as it crops up in the far corners of Europe and Africa, the virulent bird flu that raised fears of a human pandemic has been largely snuffed out in the parts of Southeast Asia where it claimed its first and most numerous victims.
Health officials are pleased and excited.
“In Thailand and Vietnam, we’ve had the most fabulous success stories,” said Dr. David Nabarro, chief pandemic flu coordinator for the United Nations.
Vietnam, which has had almost half of the human cases of H5N1 flu in the world, has not seen a single case in humans or a single outbreak in poultry this year.
Thailand, the second-hardest- hit nation until Indonesia recently passed it, has not had a human case in nearly a year or one in poultry in six months.
Encouraging signs also have come from China, although the data are harder to interpret.
These are the second positive signals that officials have seen recently in their struggle to prevent avian flu from igniting a human pandemic.
Confounding expectations, birds making the spring migration north from Africa have not carried the virus anew into Europe.
Nabarro and other officials warn that it would be highly premature to declare any sort of victory. The virus has moved rapidly across continents and is still rampaging in Myanmar, Indonesia and other countries nearby.
It could still hitchhike back in the illegal trade in chicks, fighting cocks or tropical pets, or in migrating birds.
But this sudden success in the former epicenter of the epidemic is proof that aggressive measures such as killing infected chickens, inoculating healthy ones, protecting domestic flocks and educating farmers can work, even in very poor countries.
Nabarro said he was “cautious in interpreting these shifts in patterns” because too little is known about how the disease spreads.
Other officials agreed.
“To say the disease is ‘wiped out’ there is probably too strong, too positive,” said Dr. Wantanee Kalpravidh, chief of flu surveillance in Southeast Asia for the U.N. Food and Agricultural Organization, which fights animal diseases. The governments of Thailand and Vietnam “believe they got rid of it,” she said, “but they also believe that it might be coming back at any time.”
Very different tactics led to success in the two countries.
While Vietnam began vaccinating all its 220 million chickens last summer, Thailand did not because it has a large poultry export industry and other nations would have banned its birds indefinitely.
Instead, Thailand culled wide areas around infected flocks, compensated farmers generously and deputized a volunteer in every village to report sick chickens.
It vaccinates fighting cocks, which can be worth thousands of dollars, and even issues them passports with their vaccination records so they can travel, Nabarro said.
Government inspectors sample birds everywhere; in February, Thailand reported that samples from 57,000 birds had come back negative.
According to Dr. Klaus Stoehr, a flu specialist at the World Health Organization, Thailand and Vietnam also delivered the anti-viral drug Tamiflu to even the smallest regional hospitals and told doctors to treat all flu patients even before laboratory diagnoses could be made.
Nabarro praised the leaders of the two countries for ordering high-level officials – deputy prime ministers – to fight the disease, and for making sure that enough cash to entice farmers to hand over their birds for culling flowed down official channels without being siphoned off.
Hints suggest that the disease is also being beaten back in China, the country where it is assumed to have begun. International officials tend to greet official health reports from China skeptically, in part because it concealed the outbreak of the SARS virus there for months.