Avian influenza is an infectious viral disease caused by strains of influenza A virus. It primarily affects birds.
Avian influenza strains are classified as low pathogenicity (LPAI), or high pathogenicity (HPAI) based on the severity of the disease they cause in poultry. HPAI infections are sometimes called "bird flu".
In Australia, LPAI strains are found in wild birds. These strains do not usually cause disease in wild birds. Anseriformes (waterfowl: ducks, swans and geese) and Charadiformes (gulls, terns and shorebirds) are the natural reservoirs for avian influenza A viruses.
Avian influenza viruses are complex and are grouped by 2 surface proteins: haemagglutinin (HA) and neuraminidase (NA). For example, a virus that has HA 3 protein and NA 2 protein is known as subtype H3N2. At least 16 haemagglutinins (H1 to H16), and 9 neuraminidases (N1 to N9) subtypes have been found in viruses from birds.
Avian influenza H7N8 outbreak in northern Victoria
High pathogenicity avian influenza (HPAI) H7N8 has been confirmed in northern Victoria on connected poultry properties.
This is a new outbreak and not related to the 2024 H7 outbreaks in Victoria, New South Wales and the Australian Capital Territory, which were successfully eradicated.
To find out more about the current Victorian outbreak, visit the Agriculture Victoria website.
Note: The outbreak in Victoria is not the H5 avian influenza strain impacting other parts of the world. H5 avian influenza has not been found in Australia, but bird owners can take steps to help reduce the risk to their flock when it arrives.
About avian influenza
Signs of avian influenza vary in severity depending on the strain, and vary between different species of birds. They are often non-specific signs of illness.
In poultry signs of low or high pathogenicity avian influenza can include:
- sudden death
- lethargy or reluctance to walk, eat or drink
- droopy appearance or ruffled feathers
- respiratory signs (laboured breathing, coughing, sneezing, increased nasal secretions)
- dark, thickened or dropping combs and wattles
- swelling of the head or limbs
- conjunctivitis
- nervous signs (twisted neck, inability to stay upright, uncoordinated movement, circling, partial or full paralysis)
- diarrhoea
- decreased egg laying
- soft-shelled eggs.
Poultry usually show signs of avian influenza 2-14 days after being infected. In poultry, the signs of HPAI are usually more severe and sudden than the signs for LPAI.
Testing to rule out the presence of avian influenza must be done if poultry show the following:
Layers and breeders
- a 10% drop in egg production and/or
- the appearance of unexpected shell colour or shellless eggs in 5% or more of the eggs over a 2-3 day period and/or
- mortality of 0.5% per day or more for 3 or more days in any shed and/or
- any nervous or respiratory disease signs.
Broilers
- mortality (not including culling) of 0.5% per day or more for three days or more after the first week of placement and/or
- respiratory signs lasting more than two days and/or
- nervous signs regardless of the duration.
Avian influenza is a reportable disease. If you suspect any strain of avian influenza, or see signs of disease or death consistent with avian influenza in your flock, you are legally required to report it. There are 3 ways you can do this.
- Call your local veterinarian.
- Call your closest DPIRD field veterinarian.
- Call the 24/7 Emergency Animal Disease hotline on 1800 675 888.
Avian influenza is a zoonotic disease. If you handle sick or dead birds, it is recommended to use appropriate personal protective equipment (PPE).
HPAI has occurred in poultry and backyard chickens in Australia, with 12 outbreaks of HPAI H7 viruses between 1976 and 2025.
HPAI H5 viruses have not been detected in animals in Australia. HPAI has never been detected in wild birds in Australia.
Occasionally, LPAI strains can infect poultry if the poultry:
- has contact with the saliva, nasal secretions and faecal material from wild birds infected with LPAI, or
- has contact with food, water, equipment or an environment contaminated by LPAI-infected wild birds.
People can spread the disease if they move sick or dead birds or use equipment that is not effectively cleaned between handling birds.
It is possible in certain circumstances for LPAI in poultry to mutate into HPAI.
Some endemic diseases can look similar to avian influenza such as acute fowl cholera, mycoplasma and respiratory disease complex.
Newcastle disease, which is exotic to Australia, can also look similar to avian influenza.
In the event of an avian influenza outbreak, health authorities advise properly cooked chicken meat and eggs are safe to eat. Always use good hygiene when handling raw meat and eggs.
Wild birds infected with LPAI generally show no disease signs.
Wild birds infected with HPAI may show neurological, respiratory and/or gastrointestinal signs or sudden death without prior signs. HPAI has never been detected in wild birds in Australia.