WHO declares swine flu pandemic

The Director General of the World Health Organization, Margaret Chan, has formally declared that the swine flu outbreak is now a global pandemic; the first global flu epidemic in 41 years.

In a statement, the WHO says it decided to raise the pandemic alert level from phase five to six, meaning the swine flu virus is spreading in at least two regions of the world.
The move does not necessarily mean the virus is causing more severe illness or more deaths.
So what does the declaration mean?
Dr Christopher Fraser from Imperial College London is on the World Health Organisation Pandemic Influenza Task Force.