High pathogenicity avian influenza (HPAI)

Background

Avian Influenza (AI) is a highly contagious viral infection of birds. The disease is caused by either high pathogenicity or low pathogenicity strains. Some HPAI can cause severe clinical signs and high mortality (up to 100%) in domestic poultry (chickens) and turkeys. AI in pet birds such as budgies, canaries and other caged birds has not been a feature of previous outbreaks in Australia.

Wild birds are considered the natural host for AI. Certain water birds act as reservoirs of influenza viruses by carrying the virus and spreading it to susceptible birds through contact with contaminated nasal, respiratory, and faecal material. It is not unusual for 'spill over events' to occur when AI from wild birds infects domestic poultry flocks.

Although the spread of AI from birds to people is rare, it may occur with some strains of the virus if there has been close contact with infected birds or heavily contaminated environments. This potential zoonotic risk one of the main reasons we control AI virus infections in poultry.

HPAI H5N1: The virus detected in Meredith is NOT a HPAI H5N1 virus.

Since 2021, the subtype H5N1 has spread rapidly across most continents, causing mass mortalities in wild birds and poultry. It has also caused death in some mammal populations, especially those which scavenge on birds infected with AI, such as sea lions and seals. The severity of illness, and high death rates affecting such a wide range of species is unusual in these international incidents, compared to previous outbreaks of AI.

Clinical signs of HPAI in poultry

HPAI should be considered if a high proportion of a flock or group of birds become ill very quickly – progressing from normal to severe illness or death within 24 to 48 hours. Clinical signs may include sudden death, respiratory signs (coughing, sneezing, breathing difficulties), swelling and purple discoloration of the comb or head, decreased food or water intake, decreased egg production, diarrhoea, nervous signs (occasionally seen).

Avian influenza symptoms in people

Reported symptoms in people range from very mild to typical flu-like symptoms (eg conjunctivitis, cough, fever, sore throat, muscle aches) to pneumonia and very rarely, death.

Anyone who has been in close contact with infected animals or materials, or has ‘influenza-like’ symptoms should seek medical advice immediately and contact the Communicable Disease Prevention Unit at the Department of Health on 1300 651 160 (24 hours).

There are no food safety issues identified; properly cooked chicken meat and eggs are safe to eat.

Prevention of avian influenza in birds

AI viruses can be easily transmitted from property to property by the movement of infected birds, as well as contaminated boots, vehicles and equipment. Using good biosecurity practices between and within properties and preventing contact between local water birds and poultry will lower the risk of disease spread.

People working with poultry and/or responding to avian influenza outbreaks should have a current seasonal influenza vaccine at least 2  weeks prior to coming in contact with infected birds. This will not prevent infection with avian influenza but will reduce the risk of co-infection with human influenza (‘flu’) and genetic reassortment of viruses to produce new influenza viruses that may pose a threat to the wider community.

Prevention of avian influenza in people

Appropriate use of Personal Protective Equipment (PPE) has been very effective in preventing illness. When coming into contact with potentially infected animals or materials, appropriate PPE to wear includes protective overalls, gloves and rubber boots, P2 facemask (a basic surgical mask is NOT suitable) and protective eyewear.

Further reading and more information

• Avian influenza - bird flu
• Avian influenza factsheet
• Avian influenza in people