WHO tries to allay fears over flu pandemic

THE World Health Organisation yesterday moved to dampen fears over predictions quoted by one of its own officials that a pandemic stemming from the bird flu virus ravaging parts of Asia could kill as many as 150 million people.

The UN health agency was fielding inquiries from both the media and the general public after Dr David Nabarro - a senior WHO official named on Thursday as the new UN coordinator for avian and human influenza - cited the number during a news conference at the UN's New York headquarters. WHO's flu spokesperson made a surprise appearance yesterday at the UN regular media briefing in an effort to put Dr Nabarro's comments in context.

While he did not say the 150 million prediction was wrong, or even implausible, he reiterated that WHO considers a maximum death toll of 7.4 million a more reasoned forecast.

Scientists have made all sorts of predictions, ranging from less than two million to 360 million. Others have quoted 150 million. Last year, WHO's chief for the Asia-Pacific region predicted 100 million deaths, but until now that was the highest figure publicly mentioned by a WHO official.

"We're not going to know how lethal the next pandemic is going to be until the pandemic begins," said WHO influenza spokesperson Dick Thompson.

Experts agree that there will certainly be another flu pandemic - a new human flu strain that goes global. However, it is unknown when or how bad that global epidemic will be.

It is also unknown whether the H5N1 bird flu strain circulating in Asian poultry now will be the origin of the next pandemic, but experts are tracking it just in case and governments across the world are preparing themselves for such a possibility.

Normal seasonal flu viruses have an attack rate of between 5% and 20%, but a death rate of less than 1%. Between 250,000 and 500,000 die from flu every year, according to WHO.

Based on evidence from the three pandemics that occurred during the 20th century, scientists have determined that pandemic flu strains tend to infect between 25% and 35% of the population.

The worst death rate was seen in the 1918 pandemic, known as the Spanish flu pandemic. That killed 2.6% of those who got sick, killing a total of about 40 million people.

The other two pandemics were gentler. The 1957 one killed two million people and the most recent one, in 1968, killed one million people.

Forecasts that change the assumed attack rate or the death rate will yield different predictions. Other assumptions, such as whether or not anti-flu drugs will work against the virus, also would change the figures.

The H5N1 strain of bird flu has swept through poultry populations in large swaths of Asia since 2003, jumping to humans and killing at least 65 people - more than 40 of them in Vietnam - and resulting in the deaths of tens of millions of birds. Most human cases have been linked to contact with sick birds. But WHO has warned the virus could mutate into a form that spreads easily among humans, changing it from a bird virus to a human pandemic flu strain.