Swine flu: second wave could strike with a vengeance, says WHO
Swine flu could strike with a "vengeance" in the coming months, the director of the World Health Organisation said as the number of cases across the world passed 1,000.
The WHO is considering raising its flu alert level to the top of its six-point scale, meaning that the virus has spread between different regions and a pandemic is under way.
Dr Margaret Chan, the organisation's director general, warned that a second wave of the virus is likely to be the "biggest of all outbreaks the world has faced in the 21st century", puncturing optimism that the spread may have been contained.
Last week the agency raised its alert level to five, which indicated that a pandemic was "imminent".
Dr Chan said: "Level six does not mean in any way that we are facing the end of the world. It is important to make this clear because when we announce level six it will cause an unnecessary panic."