China declared a quick victory over deadly bird flu on Tuesday, saying it had stamped out the disease in all 49 hotbeds, but gave a warning it could spread again as the weather warms up and water fowl migrate.
In Geneva, however, senior officials of the World Health Organisation (WHO) expressed caution about China's announcement, saying it thought no Asian country had yet contained the deadly virus.
Continued surveillance and checks were required in Asia, Klaus Stohr, head of WHO's influenza programme, told reporters at the start of a three-day meeting to review global preparedness for an influenza pandemic.
Avian influenza spread across much of Asia in recent months, killing at least 15 people in Vietnam, eight in Thailand and sparking fears that the region was in for a crisis on the scale of Sars. Some 100 million poultry have died or been culled.
China, which has not recorded any human cases of bird flu, said it had had no new reports among poultry for 29 days.
"The country has stamped out all 49 of the initially confirmed cases of deadly bird flu disease," Agriculture Ministry spokesman Jia Youling told a news conference.
"This symbolises that we have achieved initial results in our campaign against the deadly bird flu virus."
But he noted that there was still a risk of new outbreaks, perhaps caused by water fowl that carry the virus or by migratory birds flying north during China's spring thaw.
Other potential risks included spread of the virus from other countries or by long-distance transport of poultry. Stohr welcomed China's progress, but stressed the importance of continuing surveillance and efforts to make sure the virus is eliminated.
"We are very pleased to hear there is control progress in China and elsewhere. What is equally important to claiming success is a verification control programme...(with) which one can measure the disease being eliminated," Stohr told reporters.
Stohr noted the highly pathogenic H5N1 strain of bird flu in Asia had emerged in 1997 in Hong Kong.
"Those who have been dealing with this disease in the past are very cautious in claiming victory. Perhaps they have learned the hard way," he said.
Asked whether any Asian country had stamped out the virus, the WHO official said it had heard claims of success but so far without the data needed to back them up.
"We still don't have enough information to assess the situation in a number of affected countries. In Japan, we still have the virus active in several provinces," said Hitoshi Oshitani, director of WHO's Western Pacific Regional Office, told the talks.