The outbreak of swine flu that was first detected in Mexico was declared a global epidemic on june 11,2009. It is the first worldwide epidemic designated by the World Health Organization in 41 years.

The heightened alert followed an emergency meeting with flu expert in Geneva that assembled after a sharp rise in cases in Australia,and rising numbers in Britain,Japan ,Chile and elsewhere.

But the epidemic is"moderate" in severity,according to Mardaret Chan, the organization's director general,with the overwhelming majority of patients experiencing only mild symptoms and a full recovery, often in the absence of any medical treatment_