Can I catch chicken flu?

The avian flu epidemic in Asia shows no signs of abating. "Chicken flu", as it has become known, claimed its seventh human victim over the weekend (a six-year-old boy in Bangkok) and yesterday Pakistan announced that the virus had spread to its chicken flocks, making it the ninth country in the region to be affected.

So, how big a risk does this virus pose to human health?

As the recent deaths have shown, avian flu can jump from chickens to humans, but this is unusual and generally requires close contact with live, infected birds.

Once the virus has crossed into one human it cannot then go on to infect other humans. At present the virus spreading through Asia cannot cause an epidemic in humans, but scientists fear that that could change, given the right circumstances.

If the avian virus gets into someone who is suffering from a bout of human flu then, in theory, the two viruses could combine to form a new strain that would be both highly contagious and lethal.

Such a virus would spread like wildfire. No one would have any natural immunity to it and it would take at least a year to develop and manufacture a suitable vaccine.

Of course, the odds of someone with human flu coming into contact with a sick bird and then contracting avian flu are tiny - but they increase each time there is an outbreak in poultry.

The first recorded human case of avian flu was in Hong Kong in 1997 when six out of the 18 people who were infected died. Experts believe the current outbreak is at least the third time since 1997 that the virus has jumped species, and each time that happens there is a chance it will meet and combine with the viruses responsible for human flu.

Killer flu is nothing new - the global outbreak during the First World War claimed at least 20 million people - but we have never had to deal with a virus that can jump species, as avian flu can.

Hopefully we never will, but the recent explosion in factory farming of poultry in Asia, and the resulting increase in contact between humans and chickens, could mean it's only a matter of time before we do.

For the latest on the avian flu outbreak check out the World Health Organisation website at www.who.int