What is avian influenza (bird flu)?

Avian influenza is an infectious disease of birds, caused by a

number of different strains of avian influenza virus. Usually

the virus circulates in wild bird populations causing no

disease or only mild disease. Infection of domestic poultry,

such as chickens, can cause severe disease in these birds.

There are a number of different strains of avian influenza,

only a few of which can cause disease in humans.

A new type of avian influenza, called influenza A H5N1

(hereafter referred to as H5N1), was first recognised in 1997

in Hong Kong. This strain reappeared in late 2003 and has

rapidly spread to many Asian, Middle-Eastern, European

and African countries, causing severe infection in wild birds

and domestic poultry flocks. There is no evidence that avian

influenza is currently infecting birds in Australia.

This virus has also infected a number of people in Asia, the

Middle East and Africa who had close contact with infected

poultry or poultry droppings.

At this stage, humans infected with the H5N1 virus do not

easily transmit the infection to others. Exposure to infected

poultry, or their infected secretions or droppings, or dust or

soil contaminated with their secretions or droppings, can

result in human infection. Eating cooked poultry products

including chicken or eggs does not result in infection.

A large-scale, worldwide influenza epidemic is called a

pandemic. Pandemics occur when a new virus emerges to

which people have little or no immunity. Previous influenza

pandemics occurred in 1918-19, 1957-58 and 1968-69. In

the 1918-19 pandemic, between 20 and 40 million people

died. Many scientists are concerned that the recent H5N1

outbreak in birds could mutate to produce a new strain of

influenza virus that is easily spread among people, resulting

in a pandemic.