Very few people catch bird flu, but for those who do it is very dangerous.
In the 1997 outbreak 18 people caught it and six died. However it's extremely rare for people to catch the disease as you can only get it from a live bird in one of the affected areas.
The bird flu virus causes fever and flu symptoms in humans. They suffer from coughing fits and eventual pneumonia. Unlike Sars there are no cases of a human catching it from another human.
So why are people worried?
There is a very small chance that the virus could attach itself to a human flu virus, creating a new virus which could spread from person to person. That would be very dangerous.
If more people get bird flu the chances of a new virus forming are increased, but it will always be unlikely.