AFP - The World Health Organisation on Thursday urged people not to drop their guard over the swine flu pandemic and insisted on the value of vaccination despite the broadly mild symptoms of the virus.
"At the WHO we remain quite concerned about the pattern we are seeing, particularly because a sizeable number of people do develop serious complications and death," said Keiji Fukuda, special adviser on pandemic.
"Again, we are seeing most of this develop in people who are younger than 65 years, a picture which is different from seasonal influenza," he explained.
Fukuda reiterated that the cases of serious complications were largely found among the chronically ill, pregnant women as well as some otherwise healthy younger people.
He also countered signs of public scepticism about the vaccine revealed by surveys in several countries, despite the resurgence of swine flu in the northern hemisphere with the onset of the colder season.
"WHO believes that these vaccines are very useful against the pandemic virus," Fukuda said in a telephone news conference.
Vaccination against A(H1N1) influenza has now started in more than 20 countries and were demonstrably safe, according to the WHO.
"What we are seeing is that these vaccines are highly safe and have been received by a significant number of people without any problems," Fukuda said.
Swine flu has differed from seasonal flu in persisting in the northern hemisphere during the summer period and in a pattern of occasional serious illness affecting under 65-year-olds.
However, Fukuda acknowledged that it was as transmissible as seasonal flu, showed the same pattern of spreading more widely in winter and was "self limiting" in that the large majority of people who caught it got better without the need for special treatment.
More than 5,700 people have died worldwide since the pandemic virus was first discovered in April, with most deaths -- 4,175 -- reported in the Americas region, according to WHO data.
The United Nations World Health Organization (WHO) stated that the H1N1 virus, more commonly known as swine flu, has become the dominant flu strain in the world.

H1N1 virus.
In a briefing with reporters Thursday, WHO Special Pandemic Influenza Advisor Keiji Fukuda said the virus has been particularly active in the Northern Hemisphere in recent months. He added that he expects the trend to continue through the winter months, with more severe cases and even deaths.

Fukuda said the vaccine currently in use in some 20 countries around the world remains effective and safe, and that no rare or dangerous side effects have been reported.

"East Asia is one of the parts of the world where seasonal influenza viruses have remained in reasonably high circulation. But even in that part of the world, the pandemic virus is becoming dominant," Fukuda commented.

He noted that it was difficult to predict the activity of the virus. "We really are not going to know what the future is going to bring, and so the main focus of our effort here is ... what steps are needed to make sure countries are as prepared as possible to deal with disease levels," he said.

The H1N1 virus differs from the normal seasonal flu in that it has persisted during the summer months and affected relatively healthy people under the age of 65.  The WHO says most people recover without hospitalization, although Fuduka pointed out that people with severe health complications and pregnant women were most at risk.

The World Health Organization has declared the swine flu outbreak a pandemic. As of October 25, 2009, the WHO says there have been more than 440,000 laboratory confirmed cases of H1N1 influenza and more than 5,700 deaths reported to the UN agency.