World Health Organisation chief Margaret Chan said Tuesday it was too early to declare victory over swine flu and insisted that measures taken to deal with the pandemic were justified.

"I think that we must remain prudent and observe the evolution of the pandemic over the next six to 12 months before declaring victory," she told Swiss newspaper Le Temps in an interview.

Even though the peak of the flu has passed in some countries of the northern hemisphere, such as Canada and the United States, others countries were far from seeing the end, she noted.

"Winter is still long," said the WHO director-general, adding that a precise picture of the flu's impact would not be seen before two years.

The A(H1N1) virus has killed at least 11,516 people since it was first detected in March.

The rapid spread of the bug led the WHO to declare a pandemic in June. However, with most patients showing mild symptoms, the UN agency has been criticised by some for having over-reacted.

Chan defended the WHO's decision to declare a pandemic, saying that the UN agency adopted a "very prudent attitude" on the issue.

"I would never have declared a pandemic if I did not have the certainty of proof pointing in this direction," she said.

The WHO chief added that the agency took into account advice from independent and impartial experts.

"We are neither influenced by countries nor by the industry," stressed Chan.

She conceded however, that there was an issue with communication.

"In terms of communication, there was a big gap between the expectations and the reality.

"Everyone expected that the next pandemic would be launched by the H5N1 avian flu virus which kills 60 percent of infected people. Instead it was brought about by a more benign virus, the H1N1," she said.

Even though the swine flu pandemic has given an opportunity for countries to beef up their flu response systems, Chan said the world was not ready to deal with an avian flu pandemic.

"I say without hesitation: we are not ready at all. I really hope that the world would never have to deal with an avian flu pandemic," she said.