The World Health Organisation has raised its swine flu pandemic alert level to phase 5 - its second highest level.
The change means the agency considers the world is at imminent risk of a pandemic from H1N1 swine flu.
The virus is now confirmed in nine countries, including New Zealand.
Director General Margaret Chan made the announcement on Wednesday night in Geneva.
She said influenza outbreaks must be taken seriously because of their capacity to spread rapidly to every country of the world.
She said current stocks of the antiviral drug used to threat the virus are not enough and she urged pharmaceutical companies to increase their production capacity.
On Monday the agency raised the alert level from phase 3 to phase 4.
Up to 159 people have died in Mexico and about 1300 more are being tested. In the United States, a boy, aged 22 months, has died in Texas while on a visit from Mexico.