The H1N1 flu pandemic appears to be easing, but a third wave of infections could yet strike, the World Health Organisation (WHO) said.

"Pandemic infections are occurring in many countries but overall the pattern is decreasing," Keiji Fukuda, the WHO's top flu expert, was quoted by Reuters as saying at the start of a week-long meeting of the organisation's Executive Board.

He warned, however, that a new wave of infections could hit the northern hemisphere in late winter or early spring, saying: "This is probably the biggest speculation. We simply do not know."

The H1N1 virus emerged last April and caused the first influenza pandemic in 40 years.

It initially sparked widespread concern about antiviral and vaccine supplies, especially in developing countries, but many nations have cut back their vaccine orders recently because the pandemic has not turned out as deadly as originally feared.

WHO director-general Margaret Chan told the meeting that the effects of the pandemic had been moderate and were probably closer to outbreaks experienced in 1957 and 1968 rather than the far more deadly 1918 version.

The 1918 pandemic, known as the Spanish flu, swept around the world at the end of World War One, killing some 40-50 million people.

Chan said H1N1 appeared to be easing in the northern hemisphere, but cautioned that it was too soon to say what would happen once the southern hemisphere entered winter and the virus became more infectious.

Fukuda said the majority of people infected with H1N1 recovered without complications or special treatment, but children were being hospitalised at about twice the rate of adults.

Most deaths occurred in people with underlying conditions, including pregnancy, asthma, heart or lung disease, or diabetes. A total of 265 million doses of the vaccine had been distributed and 175 million of those administered to people, Fukuda said.

Chan, a former health director of Hong Kong, said nearly 14,000 official deaths had been reported by more than 200 countries since the virus emerged in North America last April.

But it will take at least 1-2 years after the pandemic ends to establish the true toll and WHO experts say the actual death rate could be much higher than the number of laboratory-confirmed cases so far./.