GENEVA, Switzerland (Reuters) -- The World Bank said on Wednesday that up to $1 billion would be needed over the next three years to tackle the spread of the deadly H5N1 bird flu virus.On the final day of a three-day meeting at the World Health Organization (WHO), World Bank officials said it was crucial to stamp out the H5N1 disease at source in poultry as well as prepare countries for a potential human flu pandemic.The priority under the bank's package is funding "country-owned programs," mainly for controlling bird flu in poultry through vaccines and improved surveillance.The H5N1 bird flu strain has killed more than 60 people and led to 150 million birds being culled in Asia where it is endemic in many poultry flocks.The virus remains hard for humans to catch. But scientists say that, like all influenza viruses, it is steadily mutating and could acquire the genetic changes that make it easy to pass among humans.The Asian Development Bank (ADB) also said it was making an extra $300 million available to to help fight bird flu in worst affected countries such as Vietnam, Laos, and Cambodia.Jim Adams, World Bank vice-president for operations policy and country services, presented what he called a flexible framework that would also link major international agencies."Clearly with this challenge, speed will remain critical.""I can't overemphasize the importance of equipping ourselves to respond quickly and flexibly. As problems spread across countries and if new countries are confronted with the challenge, it will be terribly important that financing can respond to those changes," Adams said.The World Bank has said its package would contain both grants or interest-free loans for countries, while half of the $1 billion will be funded by a trust financed by donors.A donor conference is set for mid-January in China, where countries will present more detailed funding needs, it said.The WHO said it needed $20 million for six months, while the U.N. Food and Agriculture Organization and World Animal Health Organization (OIE) said they were seeking $60 million in total.World Bank officials said the $1 billion figure may change."If -- and we all hope we won't have to -- we face human to human transmission, all of these figures would be multiplied by several orders of magnitude," said Fadia Saadah, sector manager for health, nutrition and population at the bank.Many poor Asian nations lack adequate surveillance and reporting mechanisms and cannot compensate farmers for poultry culls. Africa, which many experts believe will be the next front line in the fight against bird flu, faces similar problems.Officials said the estimate did not cover funding for measures in the event of widespread human-to-human transmission leading to a global human pandemic. "Cost of antivirals and vaccine are dealt with separately. Antivirals could be a very big ticket item," Saadah said.The WHO's top pandemic influenza official Margaret Chan said there were no clear figures for what it would cost for stockpiling antiviral drugs or scaling up vaccine production.Kent Hill, head of health for the U.S. Agency for International Development (USAID), said that the meeting had recognized that a "multi-faceted funding system" was needed. "Interventions will be effective in mitigating not only any H5N1 problem but any other future pandemic. Whether H5N1 hits this year, next year or the year after, these resources would be justified and make all the sense in the world," he declared.Separately, the Manila-based ADB said it had raised the amount of available funds for the region's fight against the virus to $470 million and was ready to raise it further. The ADB has already announced $170 million in grants and loans.Copyright 2005 Reuters. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.