It's too soon to conclude that the H1N1 pandemic has peaked, the World Health Organization said Wednesday.

As transmission of the virus declines in many parts of the world, WHO director general Margaret Chan asked the agency's emergency committee to review whether pandemic activity is in a "post-peak period," the time when flu activity levels return to normal levels seen with seasonal influenza.

The committee of 15 world experts advised "it was really too early to conclude that the pandemic was in a post-peak period," Dr Keiji Fukuda, the WHO's special adviser on pandemic influenza, told a news conference in Geneva on Wednesday.

The H1N1 pandemic appears to be on the less severe side of the spectrum of pandemics in the 20th century, Fukuda said.

During the post-peak period, pandemic disease levels in most countries with adequate surveillance drop below peak observed levels, according to WHO's definition. It does not mean that the pandemic is over.

On Tuesday, the committee expressed concern that the winter months in the southern hemisphere have not yet started. There's also uncertainty over whether more waves could occur, and committee members did not want to undermine preparations for this, a statement on WHO's website said.

"The director general determined that there had been no change in the pandemic phase, and decided to continue to monitor the situation and developments closely," the statement said.

Chan advised countries to continue using WHO's temporary pandemic recommendations:

• Not close borders or restrict international traffic and trade.
• Maintain surveillance for unusual flu-like illness and severe pneumonia.
• If ill, it is prudent to delay travel.

The committee will convene in the next several weeks.