WHO chief says H1N1 flu pandemic is over

GENEVA, Aug 10 (Reuters) - The H1N1 pandemic is over and the global outbreak turned out to be much less severe than was feared just over a year ago, the head of the World Health Organisation said on Tuesday.

"We are now moving into the post-pandemic period. The new H1N1 virus has largely run its course," WHO Director-General Margaret Chan said.

But the new swine flu virus, which sparked the first pandemic in more than 40 years, will continue to circulate as part of seasonal influenza for years to come, requiring health authorities to remain vigilant, Chan told a news conference.

The H1N1 virus still threatens high-risk groups including pregnant women who would benefit from vaccination against it, she said, speaking from her native Hong Kong.

Stockpiled H1N1 vaccines remain effective against the strain and so far the virus has not developed widespread resistance to the antiviral oseltamivir, the best treatment, she said.

The WHO's downgrading of the H1N1 outbreak to "post-pandemic" was based on recommendations by external influenza experts who conducted a review earlier in the day.

The United Nations agency has been heavily criticised for its handling of the first pandemic of the 21st century, which turned out to be milder than expected in most countries.

"That was the right call," Chan said on Tuesday, defending the decision taken in July 2009 on advice of the same experts.

"We need to continue to maintain our vigilance and not be complacent," she added, noting that outbreaks continued in countries including India and New Zealand.

The WHO has also firmly rejected allegations that it acted under the influence of drug companies in declaring a pandemic.

The experts' discussions by teleconference -- shrouded in secrecy -- lasted nearly three hours on Tuesday, WHO spokesman Gregory Hartl said.

Who Recommends Continued Vaccination

In June 2009, the WHO said a new swine flu virus, H1N1, that emerged in the United States and Mexico and spread around the world in six weeks, was the first pandemic since 1968. A full pandemic corresponds to phase 6 on the WHO's six-point scale for measuring the spread of a disease.

Experts analysed the level of infections in the southern hemisphere, where it is winter, and examined whether H1N1 was behaving more like a seasonal flu.

Chan said that three viruses were circulating as part of a "mixed virus pattern", typically seen during seasonal epidemics. These were H1N1 and H3N2 -- both type 'A' influenza -- as well as type 'B'.

Either H1N1 vaccine or a trivalent (triple shot) vaccine against the three strains should be used to inoculate those at risk, depending on their availability, she said.

Recent studies indicated that 20-40 percent of populations in some areas have been infected by the H1N1 and therefore have some level of immunity. Many others have been vaccinated, increasing community-wide immunity, Chan said.

The WHO's assessment of whether the disease is a pandemic or not is important for national health authorities. Chan's pandemic adviser, Keiji Fukuda, said the new status meant that governments could now scale down their surveillance and other measures.

Dozens of companies make influenza vaccines, including Sanofi-Aventis, GlaxoSmithKline, Novartis, AstraZeneca and CSL. Roche makes the frontline antiviral oseltamivir, marketed as Tamiflu.

Some 18,450 people worldwide are confirmed to have died from H1N1 infections, including many pregnant women and young people.

But WHO says that it will take at least a year after the pandemic ends to determine the true death toll, which is likely to be much higher.

Seasonal flu kills up to an estimated 500,000 people a year, 90 percent of them frail elderly people, according to the WHO. The 1957 and 1968 pandemics killed about two million and one million people, respectively, it says.