Avian influenza – information for responders
Avian influenza (AI) is a highly contagious disease affecting many species of birds including domestic poultry, which can result in significant deaths among chickens on poultry farms. The transmission of the AI virus from birds to humans is a rare event.
What is avian influenza?
Avian influenza commonly referred to as bird flu is a highly infectious viral infection of birds. The disease is caused by either highly pathogenic or low pathogenic strains. Some highly pathogenic AI viruses (HPAI) can cause sudden, high mortality (up to 100 per cent) in domestic poultry (chickens) and turkeys.
Low pathogenic AI viruses (LPAI) result in some mortality, but are often present with mild or no symptoms.
Infection has primarily been seen in domestic poultry, ducks, geese, turkeys, guinea fowl, quail, pheasants and ostriches. Many species of wild birds, including waterfowl and seabirds can carry the virus but usually show no signs of disease.
Avian influenza in pet birds such as budgies, canaries and other caged birds has not been a feature of previous outbreaks.
Influenza viruses readily mutate. Experiences from overseas outbreaks have demonstrated there is always a risk of LPAI strains (particularly H5 and H7 sub-types) mutating to more highly pathogenic forms of the virus (HPAI) in situations where the initial outbreak has not been adequately recognised or controlled.
Influenza viruses can also change and become more pathogenic through genetic reassortment. There is a small chance that if an animal or person is infected with more than one type of influenza virus at the same time, then the viruses could combine (genetic reassortment) to produce a new virus that is more pathogenic or that is able to spread more easily between people.
The risk of AI viruses infecting humans and the potential risk of new influenza viruses posing a threat to the wider community is one of the main reasons we control AI virus infections in poultry.
Can the virus spread to humans?
Avian influenza is rarely spread from birds to people. AI viruses can infect people following close contact with poultry or materials contaminated with infected poultry feathers, faeces or other waste from poultry facilities.
The transmission of the AI virus from bird to humans has been reported with some strains of the virus such as H5N1, H7N9 and H7N7es. Some AI viruses can cause severe and fatal infections in humans, however the number of human cases around the world has been small relative to the number of outbreaks in birds.
The majority of human cases have had direct or indirect exposure to infected poultry or contaminated environments. Humans infected with an AI virus do not easily transmit the infection to others. People are not infected by eating thoroughly cooked chicken meat or eggs.
What are the human symptoms of avian influenza?
The symptoms for people infected with AI viruses are similar to those for people infected with the human influenza virus, although the severity of the illness may differ. Symptoms may include influenza-like symptoms (such as cough, fever, sore throat and muscle aches), conjunctivitis (red, sore eyes), difficulty breathing and in rare cases death.
I think I have avian influenza – what should I do?
Medical advice should be sought immediately if you or anyone you have been in close contact with, experience the symptoms noted above.
This also applies if you think you have been exposed to infected materials. All incidents must be reported to your organisation’s management and the Department of Health and Human Services infectious diseases hotline 1300 651 160 (all hours).
What are the clinical signs of avian influenza in birds?
Avian Influenza is usually asymptomatic in wild birds, but can cause severe illness and death in domestic bird species. The clinical signs are variable and influenced greatly by the virulence of the viruses involved, the species affected, age, concurrent bacterial disease and the environment.
Sick birds generally exhibit clinical signs of:
- respiratory signs of coughing, sneezing or rasping breathing
- rapid drop in feed intake, water intake and egg production
- typical sick bird signs – ruffled feathers, depression, closed eyes.
In LPAI, clinical signs range from no apparent symptoms to mild or severe symptoms and usually involve the death of only small proportions of chicken flocks, ranging from three to 15 per cent.
By contrast, HPAI should be considered, if a high proportion of a flock or group of birds become ill and dies very quickly, within 24–48 hours. In addition to the clinical signs mentioned above, they may also exhibit diarrhea and/or swelling and purple discoloration of the head, comb, wattles and neck.
What do I do if I suspect avian influenza in my animals?
Note: Avian influenza is a notifiable disease. Immediately report any unusual signs of disease to your local veterinarian or Agriculture Victoria Animal Health and Welfare staff. Disease notifications can also be reported to the Emergency Animal Disease Watch Hotline on 1800 675 888 (all hours).