Bird flu (avian influenza) for health professionals

Avian influenza (bird flu) spreads to people from infected birds. It is a nationally notifiable disease. We monitor and report cases. We publish case definitions, guidelines and advice. We work with animal and environmental authorities to detect and respond to avian influenza.

For health professionals For everyone

Disease

  • Avian influenza in humans is an acute respiratory infection caused by influenza A viruses that typically infect birds.

    Like all influenza A viruses, avian influenza viruses are classified into subtypes by 2 surface proteins:

    • haemagglutinin (H)
    • neuraminidase (N). 

    Avian influenza virus subtypes – for example, H5N1 and H7N9 – are formed through different combinations of these surface proteins. 

    Each subtype differs in its ability to spread and cause disease.

    Avian influenza in humans is most often caused by:[1]

    • H5N1
    • H5N6
    • H7N7
    • H7N9
    • H9N2.

    Avian influenza viruses are further classified into genetic subgroups called clades, which help track:

    • viral evolution
    • geographic spread
    • changes in disease severity.

    For example, H5N1 clade 2.3.4.4b is closely monitored due to its potential to affect people.

    Avian influenza viruses are also classified by severity of disease (pathogenicity) in poultry, as either:

    • high pathogenicity avian influenza (HPAI)
    • low pathogenicity avian influenza (LPAI).

    HPAI and LPAI viruses can cause severe disease in people.[1][2] Whenever they are detected they require a public health response. 

    Water birds – such as waterfowl, gulls and shorebirds – are the main natural reservoir for avian influenza viruses. 

    Read more about the epidemiology of avian influenza in people.

  • Avian influenza in people causes a wide range of illness – from no symptoms to very severe disease and death.

    Signs and symptoms typically include:

    Serious complications include:

    Read more about:

Public health importance

  • Avian influenza is a public health priority globally and in Australia.

    Avian influenza in people is rare but can cause severe disease or death. 

    Although person-to-person transmission is also very uncommon, influenza A viruses mutate quickly. 

    If an avian influenza virus evolves to the point where it easily spreads from person to person, it might cause localised outbreaks and then possibly a pandemic. 

    Because of these major health impacts, we:

  • Human infections are detected sporadically across the world. Spread from person-to-person is rare, with the last documented cases reported overseas in 2007(H5N1)[3] and 2016 (H7N9)[4]. 

    Severe disease and death are most commonly reported in: 

    • H5N1
    • H5N6
    • H7N9.[2][5][6] 

    In Australia in 2010, a group of abattoir workers were infected with H10N7 and experienced conjunctivitis and mild upper respiratory symptoms.[7] 

    In 2024, Australia reported its first human infection caused by H5N1. The person was infected with clade 2.3.2.1a while travelling overseas and made a full recovery. 

    Learn more about current outbreaks in animals in Australia.

    Global spread of H5N1 in animals

    Since 2020, a global animal outbreak of H5N1 clade 2.3.4.4b has caused illness and high mortality in:

    • poultry
    • wild birds
    • several previously unaffected mammalian species. 

    Australia is the only continent free of this specific clade.

    Although infections of this clade have increased in people overseas – especially since 2024 – they remain rare. 

    Almost all cases were caused by exposure to poultry or – in the United States of America only – to dairy cattle. 

    Most human infections detected in 2024 and 2025 were mild, but some caused severe illness and death.

    The rising number of infections in mammals and people increases the risk of the virus evolving to spread among people. 

    The Australian Government is preparing a whole-of-government response in the event that  H5N1 clade 2.3.4.4b is found in animals in Australia.

Spread of infection

  • Infected animals shed the virus in respiratory droplets, faeces and other body fluids. 

    Transmission primarily occurs by:

    • inhaling infectious respiratory droplets or contaminated dust
    • touching infected animals or contaminated items or surfaces and then touching the eyes, nose or mouth.

    People are usually infected after close contact with infected poultry or contaminated areas.[8] 

    Spread from person to person is rare. 

    In specific circumstances – limited to the United States – exposure to raw milk from infected dairy cattle has caused H5N1 clade 2.3.4.4b infections in people.[9]

    There is no evidence that avian influenza can spread to people by consuming meat or eggs that have been properly handled and thoroughly cooked.[10]

  • Symptoms usually start between 1 and 10 days after exposure to the virus.

  • An infected person is considered infectious from 1 day before the onset of symptoms to 7 days after symptoms begin, or until acute symptoms resolve – whichever is longer. 

    Read more about infectious period of avian influenza.

Priority populations

Prevention

  • Annual seasonal influenza vaccination is recommended for anyone in Australia aged 6 months and over.

    Seasonal influenza vaccination does not protect against avian influenza, but it plays another important role. 

    If a person is infected with both seasonal and avian influenza at the same time, the 2 viruses can mix to form a new influenza virus that is more dangerous to people. 

     For this reason, seasonal influenza vaccination is especially important for people who:

    • work with poultry or other birds
    • travel to countries with avian influenza outbreaks.

    During a poultry outbreak, seasonal influenza vaccination is specifically recommended for commercial poultry workers.

    See:

  • Simple measures to prevent avian influenza infection in the community include:

    • washing hands thoroughly before and immediately after handling any bird (even if healthy)
    • staying away from sick or dead birds and their:
      • surrounding environments
      • droppings
      • body fluid
      • feathers
      • eggs.
    • not allowing pets to touch or eat sick or dead birds
    • calling a health professional if symptoms occur within 10 days of contact with sick or dead birds.

    Avian influenza is not a commercial food safety concern in Australia. Learn more about food safety and avian influenza. 

    If travelling

    People travelling overseas should:

    • stay away from sick or dead animals – especially birds – and any areas where they are present, including:
      • poultry farms and backyard chicken enclosures
      • areas with free ranging poultry
      • live animal ‘wet’ markets
    • ensure meat and animal products are cooked thoroughly before eating
    • not consume raw (unpasteurised) milk
    • regularly check the health advice for relevant countries on Smartraveller.

    If you find sick or dead birds

    Australia is monitoring H5 avian influenza in wild birds, poultry and other animals. 
    If you find multiple sick or dead birds or animals:

    • avoid the area
    • record your location and what you see (take photos or video, if possible)
    • report it to the Emergency Animal Disease Hotline on 1800 675 888.

  • It is especially important for people at increased risk of severe disease to:

    • stay away from sick or dead birds
    • call a health professional as soon as symptoms start, if they have been around sick or dead birds.

    Read more about tailored information for:

Diagnosis and clinical management

  • Avian influenza is diagnosed through laboratory testing.

    Nucleic acid testing is the recommended diagnostic test. Samples are usually taken from the nose and throat. If there are conjunctival (eye) symptoms, a conjunctival swab may be collected.

    Serological testing (via a blood test) may be used for public health surveillance.

    Specialised reference laboratories can perform additional testing to confirm the viral subtype and clade. 

    Triaging influenza A samples for reference laboratory testing relies on the treating healthcare professional providing key clinical and epidemiological information, such as:

    • disease severity
    • recent travel
    • contact with birds or infected people. 

    Rapid antigen tests are not recommended when avian influenza is suspected. These tests are less sensitive than nucleic acid testing and prevent subtype and clade detection. 

    Some avian influenza viruses that present a risk to people are classified as ‘highly pathogenic influenza virus, infecting humans’ under the Security Sensitive Biological Agent Regulatory Scheme.  Laboratories and other facilities handling Security Sensitive Biological Agents must follow regulatory requirements.

    Read more about:

  • Read more about laboratory testing and the laboratory case definitions.

  • Influenza antiviral treatment is recommended as soon as possible for anyone suspected to have avian influenza infection, to help prevent severe disease.

    Read more about the clinical management of avian influenza cases. 

Notification and reporting

Public health response

  • Public health authorities adopt a One Health approach to avian influenza outbreaks.

    This approach recognises how connections between people, animals and the environment contribute to avian influenza spread, including:

    • novel or endemic avian influenza viruses circulating in wild water birds
    • spillover from wild birds into poultry or other animals
    • local animal industries – such as poultry farms – that might be at risk of outbreaks.

    Key groups involved in preventing and responding to poultry outbreaks to protect animals and people include:

    • public health authorities
    • agricultural authorities
    • environmental departments
    • the poultry industry
    • landowners.

    The CDNA national guidelines for public health units inform the public health response to avian influenza outbreaks in both people and poultry. 

  • Public health authorities urgently respond to all confirmed and probable cases of avian influenza in humans, with input from an expert panel. 

    Case management focuses on:

    • identifying the likely source of infection – typically infected poultry
    • identifying and assessing contacts
    • providing education and advice on
      • when to seek further medical care
      • how to prevent onward transmission.

    Cases are recommended to isolate for at least 7 days after symptom onset or until symptoms resolve. People who are immunocompromised might need extended isolation. 

    Healthcare settings should implement extra measures when avian influenza is suspected or confirmed, including:

    • using standard and transmission-based precautions
    • using negative pressure rooms
    • seeking input from infectious disease specialists and infection control teams
    • ensuring treating healthcare professionals are vaccinated against seasonal influenza.

    Read more:

  • Public health units manage contacts by: 

    • monitoring for 10 days after their last exposure
    • providing information about symptoms, transmission and when to seek medical care
    • advising to isolate and organise urgent testing if symptoms develop
    • supporting contacts throughout the monitoring period.

    Contacts may be offered antiviral medication and asked to avoid unnecessary visits to high-risk settings – such as aged care, childcare or healthcare facilities – unless seeking medical attention. 

    Read more about contact management.

  • To date, public health responses to avian influenza in Australia have mainly been triggered by infections in poultry.

    How public health agencies respond depends on: 

    • state or territory legislation
    • the nature of the detected avian influenza virus
    • available resources. 

    See information about how public health units should respond to avian influenza outbreaks in both people and poultry.

  • Commercial poultry workers are at higher risk of being exposed to avian influenza. 

    Avian influenza outbreaks on poultry farms trigger a joint One Health response from the:

    • state or territory agricultural authority (lead agency)
    • state or territory public health authority
    • affected setting – for example, a poultry farm or producer. 

    Public health actions focus on:

    • identifying and managing people who have had contact with infected poultry
    • taking extra infection prevention and control precautions
    • tailoring heath education for affected workers
    • encouraging seasonal influenza vaccination for unvaccinated workers.

    See information on how public health units should respond to avian influenza outbreaks in poultry.

    Control measures taken by the state or territory agricultural agencies may include:

    • preventing movement of infected poultry, poultry products and equipment
    • determining the source and extent of infection
    • depopulation of affected poultry farms
    • cleaning and disinfection of contaminated equipment and environments.

    Read more in the:

Resources

References

  • 1 Center for Disease Control and Prevention United States of America, ‘Reported human infections with avian influenza A viruses’, 1 February 2024, accessed 12 July 2025.
  • 2 Xiang N, Li X, et al., ‘Assessing change in avian influenza A (H7N9) virus infections during the fourth epidemic – China, September 2015 to August 2016’, Morbidity and Mortality Weekly Report, 2016, 65(49):1390–1394,doi:10.15585/mmwr.mm6549a2.
  • 3 Wang H, Feng Z, et al., ‘Probable limited person-to-person transmission of highly pathogenic avian influenza A (H5N1) virus in China’, The Lancet, 2007, 371(9622):1427–1434,doi:10.1016/S0140-6736(08)60493-6.
  • 4 Zhang ZH, Meng LS, et al., ‘A Suspected person-to-person transmission of avian influenza A (H7N9) case in ward’, Chinese Medical Journal (English), 2017, 130(10):1255–1256,doi:10.4103/0366-6999.205849.
  • 5 World Health Organization,Cumulative number of confirmed human cases for avian influenza A(H5N1) reported to WHO, 2003–2025, 27 May 2025, accessed 8 July 2025.
  • 6 Zhu W, Li X, et al., ‘Epidemiologic, clinical, and genetic characteristics of human infections with influenza A (H5N6) viruses, China’, Emerging Infectious Diseases, 2022, 28(7):1332–1344,doi:10.3201/eid2807.212482.
  • 7 Arzey GG, Kirkland PD, et al., ‘Influenza virus A (H10N7) in chickens and poultry abattoir workers, Australia’, Emerging Infectious Diseases, 2012, 18(5):814–816,doi:10.3201/eid1805.111852.
  • 8 Badra R, Zhang W, et al., ‘Transmission pathways of zoonotic influenza viruses and influencing factors: A systematic review of recent findings’, Viruses,2025, 17(6):857,doi:10.3390/v17060857.
  • 9 CampbellAJ,BrizuelaK, et al.,‘mGem: Transmission and exposure risks of dairy cow H5N1 influenza virus’, mBio,2025, 16:e02944–24,doi:10.1128/mbio.02944-24.
  • 10 O’Brien B, Goodridge L, et al., ‘Exploring the potential of foodborne transmission of respiratory viruses’, Food Microbiology, 2021, 95:103709, doi:10.1016/j.fm.2020.103709.

We are adding new content to this website and expanding these pages, including a suite of disease-related information. In the meantime, information about diseases in Australia is available on the Department of Health, Disability and Ageing’s website.

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