The WHO chief declared here Thursday that the organization has decided to move its A/H1N1 flu alert level to phase six and the widely spreading flu has developed into a full pandemic, Xinhua reported.
Margaret Chan told a news conference that the full pandemic in 41 years was assessed as a "moderate" one.
"On the basis of available evidence, the scientific criteria for an influenza pandemic has been met. I have therefore decided to raise the level of pandemic alert from phase 5 to phase 6, the world is now at the start of the pandemic," she said.
The WHO do not suggest closing borders and urge countries do not pose restrictions on movement of people, goods and services, she said.
The chief said that more flu deaths are expected, but no sudden jump in the death toll.
She also urged to stop production of seasonal flu vaccine and turn to A/H1N1 flu vaccine production.
The decision was made following consultations with world experts through a teleconference. A WHO statement has been sent to the WHO's members.
The declaration is expected amid concerns that the A/H1N1 flu virus, which originated from Mexico two months ago, has widely spread to Asia, Europe, and the Americas.
The WHO has raised the alert level to five at the end of April, the penultimate level in its six grades, indicating a pandemic was "imminent." And many experts have been expecting the upgrade of the flu due to its fast-spreading nature.
However, experts explained that the highest level by no means indicates the greatest severity of the disease, but simply indicates the geographical spread of this flu.
This is the first global flu epidemic in 41 years. As of Wednesday, 74 countries have officially reported 27,737 A/H1N1 infection cases to the WHO, including 141 deaths.