The World Health Organization has told its member nations it is declaring a swine flu pandemic — the first global flu epidemic in 41 years.

The move came after an emergency meeting with flu experts here [Geneva] that was convened after a sharp rise in cases in Australia, which reported 1,224 cases on Wednesday, and rising numbers in Britain, Japan, and elsewhere in Asia.

In a statement sent to member countries, the W.H.O. said it decided to raise the pandemic alert level from phase 5 to 6, indicating a global pandemic outbreak, The Associated Press said, attributing the information to health officials from Scotland, Indonesia and Thailand. An official announcement of the change was due at 6 p.m. Geneva time Thursday (12 p.m. in New York).

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In an effort to avoid triggering panic with such an announcement, W.H.O. officials are expected to include with their formal announcement a caveat that the flu is not more deadly now that it has been declared a pandemic. Rather, the announcement reflects the global spread of the disease, not an increase in its severity.

According to W.H.O rules, the organization should declare a pandemic once it finds evidence of widespread “community transmission” — meaning beyond travelers, schools and immediate contacts — on two continents…

The declaration of a pandemic will trigger drug makers to speed up production of a swine flu vaccine and prompt governments to devote more money to containing the virus. While international health officials have said the flu appears to be less deadly than the annual bouts of seasonal flu that sweep the globe each year, they have warned that the virus could mutate into a more lethal strain during the southern hemisphere’s upcoming winter flu season.

Don’t panic! Yet.