5 Minute Guide: Bird flu

What happened?

Bird flu was thought to only infect birds until the first human cases came to light in 1997 when the H5N1 strain infected 18 people in Hong Kong, killing six. All the territory's poultry - over one million birds - were culled, but the virus was not eradicated.

More people were infected in China in 2003, followed by outbreaks among humans and poultry flocks around Asia over the next few years.

In 2005, the virus spread across Asia as far as the Ukraine, borne either by migrating wild birds or illegally traded poultry.

No human cases were reported outside East Asia until 2006, when H5N1 infected 12 people in Turkey, four of whom died.

In April of the same year the strain was found in a dead swan in Fife, Scotland, sparking further fears of a British outbreak.

As of June 2007, the WHO confirmed 310 cases of H5N1 in humans and 189 deaths.

Why did it happen?

There are 15 kinds of bird or avian flu, with the most contagious strains being H5 and H7, which are usually fatal in birds.

The type that is of most concern is H5N1, which can be fatal in humans.

It is thought that humans can catch the disease through close contact with live infected birds.

There may have been examples of person-to-person transmission but so far scientists say these have not been in a form that could fuel a pandemic.

What happens next?

Although no human case has been found in Europe so far, the risk is still present.

In January 2007 Taiwan conducted successful animals tests on a vaccine that could protect people against a yet-to-emerge pandemic strain of bird flu - it now hopes to conduct human trials with a view to mass production.

Several other countries are also working to develop vaccines that could be used against a pandemic.

Experts say if a pandemic bird flu strain emerges, it could take six months before inoculations can be adjusted to provide full protection.

Vaccines that defend against the existing H5N1 bird flu virus are, however, expected to provide a lesser degree of immunity.

Previous outbreaks of flu have spread rapidly across the world.

Research has shown that bird flu is similar to the 'Spanish flu', which spread rapidly through Europe after the First World War in 1918 and killed at least 50 million - more than were claimed by the war itself.

But the bird flu virus still remains hard for humans to catch and there is, at the moment, no proven human-to-human link.

In February 2007 the HN51 strain was confirmed at a Bernard Matthews poultry plant in Suffolk; some 160, 000 turkeys were culled.

At the time of writing, the Department for Environment, Food and Rural Affairs (Defra) says the strain may be identical to that found in Hungary last month, and that the most likely source of the Suffolk outbreak was wild birds.

The government insisted the risks to the public were 'negligible' - and the countryside was not closed - but the cost to Britain's poultry industry could be huge.

Key players

Dr Margaret Chan, WHO director general
She was health chief in Hong Kong during the 1997 bird flu outbreak and the SARS epidemic in 2003. She won praise for her handling of both crises.

Since her appointment as WHO boss she has warned of the imminent danger of a bird flu pandemic.

David Nabarro, the UN bird flu co-ordinator
Another former WHO official, he now heads up diplomatic efforts to combat bird flu.

He has experience of heading up the WHO's response to other difficult-to-handle situations, including the 2004 Boxing Day tsumani and the Darfur crisis.

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