Avian influenza (bird flu)

Avian influenza, commonly referred to as ‘bird flu,' is a highly contagious viral infection of birds. Serious forms of the disease caused by highly pathogenic avian influenza (HPAI) viruses can result in severe symptoms and sudden death in domestic poultry (up to 100% of birds). Mild forms of the disease caused by low pathogenic avian influenza (LPAI) viruses cause few or no symptoms in poultry and may go undetected in some species of birds, though can result in some deaths.

Avian influenza viruses are complex and are classified into subtypes based on 2 surface proteins, the haemagglutinin (HA) and neuraminidase (NA). For example, a virus that has HA 3 protein and NA 2 protein is designated as subtype H3N2. At least 16 haemagglutinins (H1 to H16), and 9 neuraminidases (N1 to N9) subtypes have been found in viruses from birds. Some specific LPAI virus subtypes (subtypes H5 and H7) can evolve to HPAI virus following spillover from wild birds and circulation in poultry.

H5N1 is a subtype of HPAI which is causes serious disease in poultry, wild birds and some species of wild mammals globally. It has not been detected in birds in Australia to date.

Domestic poultry, ducks, geese, turkeys, guinea fowl, quail, pheasants, emus and ostriches are most susceptible to being affected by avian influenza. Many species of wild birds, including waterfowl and seabirds can carry the LPAI virus but usually show no signs of disease.

All bird species are thought to be susceptible to HPAI H5N1, and it has been detected in over 50 species of mammals.

Wild birds are considered the natural host for the virus. In Australia, some wild birds carry LPAI but usually do not show any symptoms of the disease.

Infected birds shed the avian influenza virus in saliva, nasal secretions and faeces.

Sometimes the virus spills over from wild birds into domestic bird populations and may cause disease. This can occur through either direct contact between wild and domestic birds, or indirectly through contamination by wild birds of feed or water of domestic birds.

With the emergence of HPAI H5N1 internationally, many animal species have become infected following close contact with infected birds or contaminated environments. Consumption of infected bird carcases has resulted in the transmission of H5N1 to some predatory and scavenger species.

Symptoms associated with avian influenza can include:

• sudden death
• respiratory signs (noisy or rapid breathing, coughing, sneezing, increased nasal secretions)
• conjunctivitis
• swelling of the head
• purple discolouration of the comb and wattles
• rapid decrease in feed and water intake
• decreased egg production
• ruffled feathers
• depression
• closed eyes
• diarrhoea
• nervous signs (twisted neck, inability to stay upright, inability to fly, uncoordinated movement, walking or swimming in circles, partial or full paralysis).

All bird owners need to be vigilant for any signs of avian influenza in their flocks.

Avian influenza is a notifiable disease. This means that legally you must tell us if you know of or suspect the presence of avian influenza in any birds.

You can do this by immediately calling one of the following:

• Agriculture Victoria on 136 186 (Monday–Friday, 8 am – 6 pm)
• the VicEmergency Hotline on 1800 226 226.

Good biosecurity practices are essential to reduce the risk of disease. For more information please see:

• Biosecurity for poultry producers
• Keeping backyard poultry

The spread of avian influenza from birds to people is rare but may occur with some strains of the virus if there is close contact with infected birds or their droppings, or with heavily contaminated environments. Always practice good personal hygiene when handling birds.

People cannot become infected by consuming cooked chicken meat or eggs.

If you have had contact with birds on an affected property and you are experiencing cold or flu symptoms, call your doctor or the Department of Health on 1300 651 160 for medical advice.

Find out more about avian influenza in humans from the BetterHealth Channel.

Ongoing outbreaks of H5N1 globally have increased the level of risk to Australia for incursions of HPAI viruses of global concern.  Occasional outbreaks of internationally notifiable highly pathogenic avian influenza (non-H5N1) and of low pathogenicity avian influenza have occurred on poultry farms in Australia.

Each outbreak was quickly detected and eradicated, with only a small number of farms affected.

Annual migration of wild birds has the ongoing potential to introduce new subtypes of avian influenza virus to Australian birds.

State and Commonwealth governments and the national chicken meat, duck meat and egg industries have formal arrangements in place to share the costs of responding to outbreaks of highly pathogenic avian influenza and low pathogenic avian influenza (H5/H7 virus subtypes only). This helps ensure a rapid and effective emergency response can be immediately mounted if the disease occurs.

Owners may be eligible for compensation if birds or property must be destroyed to eradicate the disease.

Procedures for responding to outbreaks generally include:

• euthanasia  of infected and in-contact poultry (depopulation)
• decontamination
• strict quarantine
• movement controls to prevent spread of infection
• tracing and surveillance to locate the extent of infection.

Vaccination might be an option in some circumstances but there is no vaccine currently available in Australia.

Nine outbreaks of HPAI have occurred on poultry farms in Australia between 1976 and 2021: in Victoria in 1976, 1985, 1992 and 2020; in Queensland in 1994; and in NSW in 1997, 2012 and 2013. On each occasion, the outbreaks were quickly detected and eradicated, and only a small number of farms were affected. Effective eradication measures ensured that Australia has remained free of HPAI.

In 2020 and early 2021 Agriculture Victoria worked with the poultry industry and the community to control and eradicate outbreaks of avian influenza.

There were 3 different strains of avian influenza, across 3 local government areas during this incident:

• 3 egg farms with highly pathogenic H7N7 avian influenza
• 2 turkey farms with low pathogenic H5N2 avian influenza
• 1 emu farm diagnosed with low pathogenic H7N6 avian influenza.

Proof of freedom of the disease was declared internationally on 26 February 2021.

Surveillance of both domestic and wild birds was a key part of the response and is ongoing.

The ongoing surveillance activities mean we are confident that the virus is no longer present on the farms or in surrounding areas.

A wild bird surveillance program is in place across Australia, supported by Wildlife Health Australia.

Report an unusual sign of disease or death in wild birds.