Girding up to fight a potential flu pandemic that could kill tens of millions of people worldwide, the United Nations health agency has appealed to wealthy countries to help it build up a stockpile of antiviral medicine that it could rush to regions in need, especially to poorer nations, in view of current bird flu outbreaks.

"Right now, many wealthy countries are creating their own stockpiles of antivirals. However, poor countries simply cannot afford to do this," UN World Health Organization Director-General Lee Jong-wook said in welcoming a donation to its rapid-response stockpile of 3 million treatment courses of the antiviral oseltamivir from the Roche company.

"If a flu pandemic were to emerge in a poor country for example, these drugs could be flown quickly to the centre of a potential pandemic. We urge other countries to help us build up the international stockpile," he told a news conference in Geneva.

"Preparing the world for a pandemic strain of influenza is a WHO priority. It must also be a priority for every country in the world. Coordinated and effective action can reduce the death, suffering and social disruption a pandemic would otherwise cause," he said.

Ever since the first human case of bird flu, linked to widespread poultry outbreaks in Viet Nam and Thailand, was reported in January last year, WHO has warned that the virus, H5N1, could evolve into a global influenza pandemic if it changes into a form which could transmit easily between people. The so-called Spanish flu pandemic of 1918-1920, unrelated to the present virus, is estimated to have killed between 20 million and 40 million people worldwide.

In the agreement signed here, Roche has committed to providing 3 million treatment courses which would be dispatched to people in greatest need at the site of an emerging pandemic.

Oseltamivir could help to reduce illness and death, and when combined with other measures, could potentially contain an emerging pandemic virus or slow its national and international spread. If it reaches the site of an outbreak quickly, an antiviral stockpile could especially help people in poorer countries, said the WHO release.