The United Nations' top official on bird flu urged China to share its experience with other countries on how to tackle the disease.

Speaking at the end of his third visit to China as UN coordinator for avian influenza, David Nabarro said he had tried to persuade Chinese officials that the knowledge and experience they gained fighting bird flu could help the rest of the world.

"Perhaps the most important thing that I would wish to happen is that Chinese officials at all levels who have been working on this issue for many, many months ... have a chance to interact with colleagues from governments who are just beginning to struggle, to share with them some of the trials and tribulations they have faced," Nabarro told reporters.

China had the world's largest poultry population, with 20 percent of the global total, UN officials said.

It had an estimated 50 percent of the world's pigs and 90 percent of the world's geese, they said. The virus is carried in these animals as well as other poultry and wild migratory birds and is spread to humans through close contact.

China had also undertaken the world's biggest vaccination campaign, pledging to vaccinate all of its 14 billion poultry.

"I think there's a lot that the world can learn from China," Julie Hall, the UN coordinator for avian influenza in China, told the same news conference.

Nabarro visited China to take stock of what it has done and persuade it to contribute its expertise and information to the global bird flu fight. He said he was "pretty satisfied" with the government's handling of the disease.

But he added: "It's a long haul. This virus is not going to disappear suddenly."

Nabarro pointed to the "enormously rapid" spread of the H5N1 bird flu virus in the past three months, including to Africa, Europe and the Middle East, which made international cooperation crucial.

He noted that while 15 countries reported bird flu outbreaks in the past two and a half years, the figure increased to 30 countries in the past two and a half months.

China has agreed to share a batch of virus samples from its poultry outbreaks. The shipping process and logistics were being worked out. Officials expected the samples to be sent within days.

UN officials, however, emphasized they would like to see China share more consistently, especially as the virus was changing and scientists need to study it and find answers to many unanswered questions.

"We need to share information and samples in a timely manner, in a regular manner and also globally," said Henk Bekedam, the World Health Organization's China representative.

China has reported 11 deaths from bird flu out of 16 human infections and 34 outbreaks of bird flu among poultry since the beginning of last year.

No poultry outbreaks have been reported in China since late February. The warmer weather, the poultry vaccination campaign and precautionary measures may have contributed to fewer outbreaks, said Hall, the UN coordinator.