Bird flu is the common term used for avian influenza. The H5N1 virus causes it.
The H5N1 virus, also known as the highly pathogenic avian influenza virus of type A of subtype H5N1, is a highly infectious and severe respiratory disease in birds, which may spread to humans and animals.
According to the World Health Organisation, the H5N1 virus occasionally occurs in humans, albeit with a 60% chance of survival. The disease does not, however, infect humans easily. Any infection in humans results from close contact with secretions such as mucous, droppings, or saliva from infected birds.
Human to human spread of the virus is rare and occurs only in extremely close contact cases, such as what happened when a mother was looking after her infected child. Contrary to popular belief, the disease does not pass through food or the eating of eggs cooked at high temperatures.
There is widespread worry over the H5N1 virus because the virus may mutate and become easily spreadable among humans. When this occurs, the high mortality rate can become a cause for public health concerns.