The World Health Organization declared the first flu pandemic of the 21st century, Sweden's health ministry said.

The health ministry said the United Nations agency was raising its pandemic flu alert to the top phase 6 on a six-point scale, indicating the first influenza pandemic since 1968 is under way.

WHO Director-General Dr Margaret Chan was due to give a news conference on the influenza (A) H1N1 pandemic at 1600 GMT, following a meeting of the WHO's emergency committee of flu experts, and WHO spokesmen declined to comment before that.

The move will trigger heightened health measures in the WHO's 193 member states as authorities brace for the worldwide spread of the virus that has so far caused mainly mild illness. The move to phase 6 reflects the fact that the disease, widely known as swine flu, was spreading geographically, but not necessarily indicate how virulent it is.

"Phase 6, if we call a phase 6, doesn't mean anything concerning severity, it is concerning geographic spread ... Pandemic means global, but it doesn't have any connotation of severity or mildness," WHO spokesman Gregory Hartl said.

David Heymann, a former top WHO official now chairing Britain's Health Protection Agency, said that countries had tried to contain the virus through measures including school closures during the previous phase 5. This has extended the precious time needed to prepare for a full-blown pandemic.

As it spreads in humans, science cannot predict what course the virus will take, the disease it causes and the age groups infected, Heymann said. "The severity of that disease, the effectiveness of antiviral drugs and the stability of the virus must all be watched closely," he added.

Argentina's Health Minister, Graciela Ocaña, confirmed 62 new swine flu cases in the country, which adds up to 343 cases since the illness outbreak.

Meanwhile, 1,211 possible H1N1 samples are being tested in Malbrán Institute and 39 samples were negative.
"We will continue with the experts committee meetings to analyze the actions according to this pandemic flu and we will issue the WHO recommendations," said Health Minister Ocaña.

Ocaña said they will suspend school classes as necessary in order to prevent the spread because "it's been successful" and educational facilities are the main place of infection. She also suggested "social self-isolation" to those who have H1N1 symptoms or who travelled to ant country with Influenza outbreak.

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