The World Health Organization says public-health officials and governments worldwide should be preparing for a possible global influenza outbreak - a health emergency that could kill millions of people.

Experts from 11 countries - including representatives from vaccine manufacturers and health laboratories, regulatory authorities and health ministries - issued the warning at a two-day meeting in Geneva on how to prevent a future pandemic - a worldwide outbreak of disease with possibly catastrophic consequences.

The last two flu pandemics occurred in 1957 and 1968. Both caused millions of deaths, although they were smaller in scale than the worst flu outbreak in modern history, which killed up to 50 million people early in the 20th century, just after World War I, in 1918-1919.

The U.N. health agency says another pandemic could develop rapidly if a virus such as the bird flu currently found in parts of Asia abruptly mutates to a form that threatens widespread human infection.

WHO warns it could take drugmakers up to six months to develop a vaccine against such an outbreak, and it says national health authorities must begin cooperating now on testing and licensing issues and other procedures.

At the Geneva meeting, which ended Friday, the WHO official in charge of global influenza program, Karl Stohr, said the organization is counting on rich countries and medical research foundations to finance vaccine testing over the next 12 months - expected to cost under $15 million.

Some information for this report provided by AP.