Swine flu set to spread, as cases surge: WHO

Swine flu will spread further across the world, experts at the World Health Organization warned Friday, as the number of confirmed cases surged by more than a thousand in 24 hours.

In Geneva, acting WHO Assistant Director-General Keiji Fukuda told reporters that studies by experts indicated a "significant number of people" had been infected but remained undetected or unconfirmed by laboratory tests.

"Their work also suggests that the virus is transmissible enough that we will expect to see continued community level outbreaks and regional spread," he told a WHO meeting in Geneva on pandemic preparedness.

New cases reported

The latest WHO data showed 7,520 people in 34 countries were confirmed to have caught the influenza A(H1N1) virus, 1,000 more than a day ago.

According to the figures, most of the deaths had occurred in Mexico, with four in the United States and one each in Canada and Costa Rica.

WHO Director-General Margaret Chan noted the virus had "quickly demonstrated its capacity to spread easily from one person to another, to spread widely within an affected country and to spread rapidly to additional countries."

"We expect this pattern of international spread to continue," she said.

"This is a time of great uncertainty, and great pressure on governments, ministries of health and WHO," she added.

Fresh updates continued to come in from governments around the world.

Mexican Health Minister Jose Angel Cordova announced two more deaths there, bringing the country's total number of fatalities to 66, with 2,829 infected, but reported that the rate of infection there continued to fall.

Their work also suggests that the virus is transmissible enough that we will expect to see continued community level outbreaks and regional spread

Keiji Fukuda, WHO

It was a different story in the United States where health authorities said the number of confirmed cases of swine flu had jumped from 3,352 to more than 4,714 spread across 46 out 50 states.

On Friday, New York City authorities closed three schools, sending home 4,500 students, after the assistant principal of one of the schools was hospitalized in a serious condition.

Four students in the Queens district of the city were also reported to be infected with swine flu, said New York mayor Michael Bloomberg and there were "an unusually high level of flu-like illnesses."

Less than two weeks earlier, city authorities had pronounced the all-clear after other schools were affected by the virus through students who had visited Mexico.

Ambiguous virus

Fukuda said the behavior of the virus would also change depending on "whether it is winter period in one part of the world or another."

The virus had "a very different pattern" from normal, seasonal flu, warned Fukuda: half of those who had died had been young and otherwise healthy adults.

"Right now we don't know what the future will bring," Fukuda said.

Pharmaceuticals giant GlaxoSmithKline meanwhile said they would start developing nearly 130 million doses of a vaccine for France, Belgium, Britain and Finland as soon as the WHO had provided the "virus seed" -- a medical breakdown of the new disease.

Right now we don't know what the future will bring

Fukuda

Britain's health ministry said they had also reached agreement with U.S. drugs manufacturer Baxter to develop a vaccine before any pandemic begins.

Baxter said it was working with virus strains provided by the U.S. Centers for Disease Control and Prevention (CDC) to produce a vaccine.

Belgium announced two new cases, bringing the total infected there to four.

And Norway lifted its advice against travel to Mexico, in line with the WHO's position. The country has registered two mild cases of swine flu in two young students back from Mexico.