The world is now much better prepared to deal with a possible pandemic than five years ago, a senior World Health Organization (WHO) official said on Sunday.

"The past five years have put us in the best possible position to handle this kind of situation," Keiji Fukuda, acting WHO director-general for health security, told a telephone press conference on the current threat of swine flu.

Fukuda said the world had been dealing with the threat of bird flu in the past five years and that was helpful for facing the current threat from swine flu.

According to the official, the swine flu virus, which have killed 81 people in Mexico and caused cases in the United States and several other countries, could mutate into a more dangerous strain.

But WHO experts need more information to decide whether it's necessary to raise the current pandemic alert level, which is still at phase 3, indicating no or very limited human-to-human transmission, he said.

A WHO emergency committee is scheduled to re-convene on Tuesday to assess the situation and advise WHO Director-General Margaret Chan for responses, he added.

On Saturday, the committee, which is composed of international experts, concluded that the current swine flu situation "constitutes a public health emergency of international concern."

The WHO chief recommended, on the advice of the committee, that all countries intensify surveillance for unusual outbreaks of influenza-like illness and severe pneumonia.

At the teleconference on Sunday, Fukuda also said there is currently no evidence the swine flu outbreak in Mexico represents an attack of bioterrorism.

"There are no signs we are dealing with purposeful actions," he said, in response to a question about US President Barack Obama's recent visit to Mexico.

Fukuda also said that WHO currently has no evidence that people can be infected with swine flu through exposure to pork.