The World Health Organization has raised its pandemic alert for H1N1 influenza to Phase 5 - the second highest level - meaning that it believes a global outbreak of the disease is imminent.
WHO Director-General Margaret Chan declared the Phase 5 alert Wednesday after consulting with flu experts from around the world.
The decision could lead the global body to recommend additional measures to combat the outbreak.
Those measures include vaccine manufacturers switching production from seasonal flu vaccines to a pandemic vaccine.
A Phase 5 alert means there is sustained transmission among people in at least two countries.
Once the virus shows effective transmission in two different regions of the world a full pandemic outbreak would be declared.
