Avian influenza (bird flu)

Notification requirement for avian influenza

Medical practitioners and pathology services should immediately notify any suspected or confirmed cases to the Department of Health by telephone on 1300 651 160 (24/7). Pathology services must follow up with written notification within 5 days.

Primary school and children’s services centre exclusion for avian influenza

Cases should be excluded until no longer infectious as advised by the Local Public Health Unit.

Infectious agent of avian influenza

AI viruses can be classified into 2 forms based on the severity of disease in birds:

• Low pathogenic avian influenza (LPAI)
• Highly pathogenic avian influenza (HPAI).

LPAI strains are mild and usually cause few clinical signs in chickens/poultry. HPAI strains can cause severe disease and high mortality in infected poultry.

HPAI and LPAI designations do not correlate with the severity of illness in humans. Both LPAI and HPAI viruses have caused mild to severe illness in infected humans.

Identification of avian influenza

Clinical features

Human infections with AI may be asymptomatic, or present with mild symptoms such as conjunctivitis, upper respiratory symptoms, or flu symptoms that can include:

• fever
• chills
• cough
• sore throat
• muscle aches
• shortness of breath
• coryza
• fatigue
• headache.

Less commonly reported have been gastrointestinal symptoms, including diarrhea, nausea and vomiting. Severe disease can result in pneumonia, neurological changes (e.g. seizures), and encephalitis.

Diagnosis

Laboratory confirmation should be sought urgently to confirm all suspected cases. All suspected cases should be discussed with the relevant Local Public Health Unit who can provide advice on testing and coordinate with the laboratory.

Diagnosis of AI is typically confirmed via nasopharyngeal and throat swabs using polymerase chain reaction (PCR) for AI, and viral culture and PCR for influenza. The swabs may induce coughing and should be collected in a negative pressure room if available, or in an open air environment using appropriate personal protective equipment (PPE) if not available. Implement airborne, droplet contact transmission-based precautions when providing care for anyone suspected or confirmed to have AI. Appropriate PPE includes gloves, gown, protective eyewear and a P2 or N95 respirator.

Swabs should be sent directly to the Victorian Infectious Diseases Reference Laboratory (VIDRL) for urgent testing.

Incubation period of avian influenza

The incubation period for AI will typically range from one to 10 days. This may vary depending on the AI strain.

Public health significance and occurrence of avian influenza

AI viruses pose a risk to human health due to their potential to cause severe illness in people, and their pandemic potential if they adapt to spread easily from person-to-person.

Several AI outbreaks have previously occurred in Australia among commercial flocks of birds. In May 2024, Australia reported its first human case of H5N1 avian influenza in a returned overseas traveller.

Reservoir of avian influenza virus

Wild birds are considered the natural host for the virus. 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.

Mode of transmission of avian influenza virus

Most people are not at risk, as AI viruses do not spread easily from birds to people. Even with the highly pathogenic H5N1 AI strain, which many people have been exposed to globally, very few human cases have been recorded. People who have close or prolonged unprotected contact with infected birds or animals or their contaminated environments are at greatest risk of infection.

Although limited human-to-human transmission of avian influenza viruses may have occurred in some instances with close or prolonged contact with an infected person, sustained human-to-human transmission has not been identified to date.

People cannot be infected with AI through eating fully cooked poultry or eggs, even in areas with an outbreak of AI.

Period of communicability of avian influenza

The infectious period for AI in humans may be longer than for normal seasonal influenza and vary depending on the AI strain. No detailed studies have been conducted of infectivity of AI viruses in humans.

Susceptibility and resistance to avian influenza virus

Routine seasonal influenza vaccination does not protect against avian influenza. However, it is possible that if a person is co-infected with avian or swine influenza and a strain of human influenza virus, the 2 strains could genetically reassort and form a more virulent or more transmissible strain with pandemic potential. Influenza vaccination is therefore recommended for commercial poultry workers during an outbreak of avian influenza.

Control measures for avian influenza

Preventive measures

People travelling to areas affected by AI are at very low risk of infection. This risk can be reduced further by:

• avoiding poultry farms and live bird 'wet' markets
• avoiding contact with wild or domesticated birds
• washing their hands thoroughly after handling birds and uncooked poultry products such as meat or eggs
• ensuring poultry or poultry products are cooked thoroughly before eating.

To minimise the risk of exposure to anyone working with potentially infected birds, good occupational health and safety practices should be followed. See Agriculture Victoria's Avian Influenza factsheet for more information.

Control of human cases

Treatment is the responsibility of the treating medical practitioner in consultation with an infectious diseases specialist. Antiviral medications have been shown to attenuate disease in cases of seasonal influenza and may also be effective for treating AI. It is recommended to initiate antiviral treatment with a neuraminidase inhibitor as soon as possible even if more than 48 hours has elapsed since illness onset and regardless of illness severity.

Cases should be isolated until they are no longer infectious as advised by the Local Public Health Unit. Hospitalised cases should be managed in a negative pressure room if available under airborne, droplet and contact precautions in addition to standard precautions.

The Department of Health investigates all suspected cases of avian influenza to confirm the diagnosis and follows up confirmed cases to investigate the source of infection, identify other cases, identify and protect susceptible contacts, and prevent onward transmission in the community.

Control of human contacts

For all people identified at risk, education is provided by the Local Public Health Unit. Contacts are requested to monitor for symptoms of AI. As incubation periods may vary, the self -monitoring period will be determined by the Local Public Health Unit. Should contacts become unwell, they are advised to isolate and report their illness to their Local Public Health Unit who will facilitate testing and post-exposure prophylaxis (antivirals) if required.

Control of environment

Avian influenza is a notifiable exotic disease in birds and any suspected or confirmed cases must be reported immediately to Agriculture Victoria.

Outbreak measures for avian influenza

If human cases are suspected in Victoria, the Local Public Health Unit and the Department of Health will work with the patient, treating doctors, and the laboratory to confirm the diagnosis. Cases will be isolated from others to prevent further transmission.

Close contacts of cases will be counselled about the risk of infection and monitored by the Local Public Health Unit. If they develop symptoms, they will also be advised to isolate and be tested for AI.

In Victoria, animal health authorities (Agriculture Victoria) will investigate and respond to AI outbreaks in poultry farms. People who have been exposed to infected birds during an outbreak will be followed up by the Local Public Health Unit to monitor for symptoms.