Health experts will review the status of the H1N1 pandemic in a few weeks to decide whether it has peaked but it is already clear that it is less severe than previous outbreaks, the World Health Organisation said.

The WHO's emergency committee has decided that it was premature to declare the pandemic, which was declared in June and was the first in more than 40 years, was past its worst.

The 15 members of the body that makes confidential recommendations to WHO Director-General Dr Margaret Chan deliberated for two hours but decided there were too many uncertainties about how the pandemic was behaving, even if it appeared to be subsiding in North America and Europe.

Dr Keiji Fukuda, the WHO's top influenza expert, told reporters on Wednesday that rising levels of infection in West Africa and the risk posed by the winter months in the southern hemisphere were the dominating concerns of the committee.

'We have some reason to be concerned about what may develop as half of the world goes into its winter months,' Fukuda said.

He said the United Nations health agency had confirmed reports of rising infection in Senegal and Mauritania, and was checking to see whether the flu virus was spreading in other parts of West Africa.

Fukuda urged people and governments not to let their guard down even though the current swine flu outbreak has not been as harsh as pandemics that killed millions over the past century.

'This pandemic appears to be on the less severe side of the spectrum of pandemics that we have seen in the 20th century,' he said.

Over 16,000 confirmed deaths

So far the WHO has confirmed 16,226 deaths attributable to the H1N1 pandemic virus, but the real death toll -- which will take a year or two to ascertain -- will be much higher, as many victims have so far not been diagnosed with the flu strain.

People should continue to seek vaccination against the pandemic, which is dangerous for young adults, especially those with chronic health conditions, and pregnant women, in contrast to seasonal strains where the elderly are vulnerable, he said.

Fukuda said over 300 million people have now been vaccinated against pandemic influenza, and the shots, which have an excellent safety record, have proved 70-75 percent effective.

The pandemic sparked a race to develop new vaccines by drug makers such as GlaxoSmithKline and Sanofi-Aventis but many people have not taken the vaccine as the outbreak has turned out to be fairly mild.

A decision by the WHO emergency committee that the pandemic has entered a 'post-peak' phase will indicate to governments and health authorities that the virus, while still a global pandemic, is in a transition to a more normal state of affairs where it circulates as seasonal influenza.

That would enable authorities to revise their emergency health arrangements. – Reuters