Birds can catch the virus we know as flu just like humans, dogs, horses and pigs. Each species tends to have its own particular viral strains, and bird flu generally affects domesticated poultry and wild birds.
Why is bird flu in the news in recent months?
Flu strains that affect one species can sometimes jump across to another. This happens when close proximity to affected animals, usually poultry or pigs, allows human flu strains and animal strains to combine to form entirely new flu strains.
A new bird strain, known as H5N1, has emerged and spread via wild birds from the Far East across central Asia as far as Turkey and Romania. It is highly dangerous to poultry but has also infected and killed humans.
How many humans have been affected?
There have been about 157 human cases involving the H5N1 strain. Frighteningly, about 50 per cent of all those who contracted the strain have died. The deaths have included otherwise healthy young people who can usually tolerate the more common flu strains.
This sounds very dangerous. Should be we panicking?
No need to panic yet. All of those affected got the virus from infected poultry directly and apparently not from other humans.
While H5N1 can move from birds into humans, the virus does not readily do so. Only people in close contact with large numbers of infected birds seem to catch H5N1.
Why is H5N1 so deadly?
It causes severe symptoms and progressive respiratory failure, often with multiorgan failure. This occurs even in healthy young people, not just in the elderly or very young as with most human influenzas.
So how do you catch this flu and why is it different from other influenzas?
You must be in direct contact with infected birds, their droppings or feathers. So far H5N1 does not seem to have mixed with human flu strains to produce a new mutant that is easily caught by humans.
Most influenzas are highly contagious and are quickly spread by casual contact and droplets from sneezing.
Being a flu of birds, H5N1 does not have the characteristics that would enable it to move quickly through human populations - at least not yet.
Could this strain change to something more dangerous?
Yes, it could, and this is why H5N1 is in the news and why governments have prepared for its possible arrival. The more humans that get the H5N1 strain, the greater the chance that it will mix with a human flu and mutate to form a dangerous new flu that can easily infect humans.
Humans have not experienced this flu before, so we have no natural immunity to it. If it mutated to a human compatible form and remained as dangerous, then it could cause a worldwide pandemic.
We do not know if such a mutation will ever occur, and have no way of knowing whether any recombination will remain as dangerous as the original H5N1. But flu recombinations are a frequent occurrence and have caused pandemics in the past, including the 1918 Spanish flu which killed up to 40 million worldwide.
Can you get H5N1 from eating chicken or eggs?
Thoroughly cooked eggs and poultry are perfectly safe. Raw eggs or undercooked meat from infected poultry could potentially cause infection, but the real risk seems to be close proximity to infected birds, not consumption of them.
Should I avoid travelling to Turkey?
H5N1 hasn't yet made the jump into humans, so you are currently only at risk if you go on to poultry farms or handle live or dead birds there. The same holds true of other places where bird flu has infected humans including Cambodia, China, Indonesia, Thailand, Vietnam and Russia.
Will H5N1 reach Ireland?
Probably, via migratory birds which catch and spread the flu among one another just as humans do. The question remains whether the H5N1 bird flu will be able to make the jump into humans. Very few humans have caught the strain despite so many people in so many countries being in close proximity to infected birds.