At least 254,000 laboratory confirmed cases of H1N1 virus has been reported from all over the world, which means that actual number could be much more, WHO's Gregory Hartl said at a news conference in Geneva.

"With the virus circulating so widely around the world, it is unfortunately to be expected that there will be deaths as the volume of cases and deaths is increasing," he said.

At the same time, there is no indication that the virus has mutated or changed its behaviour, he said noting that the virus is not causing more severe illness than before.

According to the latest update issued by WHO, tropical regions of South and South-East Asia continue to experience geographically regional or widespread influenza activity in India, Bangladesh, Myanmar, Thailand, Cambodia, Sri Lanka and Indonesia.

Many countries in the region are reporting increasing or sustained high levels of respiratory disease, and a few, including Thailand and Brunei Darussalam, have begun to report a declining trend in the level of respiratory diseases.

Although many countries in temperate regions of the southern hemisphere (Chile, Argentina, Australia, and New Zealand) have passed the peak of their winter influenza epidemic, sustained influenza activity continues to be reported in South Africa and in the southern and western parts of Australia, the WHO noted.

Meanwhile, in Canada and the United States, influenza activity remains low overall. However, regional increases are being detected in the south-eastern United States.