Avian influenza (bird flu): The basics

  • Avian influenza (AI) is a disease of birds, not humans. People can become infected but rarely are. There are many strains of avian influenza viruses which vary in their ability to cause disease.
  • AI viruses are categorized according to this ability to cause severe disease (pathogenicity) in avian species as either highly pathogenic avian influenza viruses (HPAI) or low pathogenic (LPAI).
  • The symptoms of HPAI are respiratory distress, swollen heads, dullness, a loss of appetite and a drop in egg production.
  • LPAI does not always cause obvious disease in birds. It is thought that influenza viruses circulate freely in the global wildfowl population.
  • Unlike FMD, AI is not an air-borne disease. AI is spread by movement of infected birds or contact with respiratory secretions, and in particular faeces, either directly or through contaminated objects, clothes or vehicles.
  • Some strains of HPAI spread easily and quickly between birds in poultry populations and cause severe disease, with a high death rate.
  • In rare cases, some HPAI strains have lead to severe disease and deaths in people where infection has resulted from close contact with infected birds.
  • There is a limited number of reported cases of person to person spread of AI, but no evidence of sustained transmission between people.
  • AI viruses can exchange genetic material with human influenza viruses in humans or susceptible animals to emerge as new viruses which may be capable of being spread easily between people. This is what makes AI a potential threat to public safety.
  • The global human population may have little or no immunity to a new influenza virus that significantly differs from recent or existing strains of human influenza viruses. So any outbreak of AI must be controlled quickly and workers and veterinarians in close contact with infected birds must be well protected. The Government has contingency plans in place to ensure this can be achieved.

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Page last modified: November 3, 2009