Avian Influeza Disease Information

Avian influenza viruses commonly known as bird flu, naturally circulate in wild aquatic birds such as ducks and shorebirds and their transmission and circulation in farmed poultry impose threats to poultry production, food security and global economy.

Avian influenza viruses are members of the family Orthmyxoviridae, Type A which is subdivided into categories (strains) depending on their outer proteins H (Haemagglutinin) and N (Neuraminidase). These outer proteins can be combined to create different strains, for example H5N1, H9N2. Influenza viruses have a single stranded RNA genome that is spilt into eight different segments, which are surrounded by a capsid and an envelope. These viruses continually evolve through genetic reassortment and mutation/drift and gain ability to overcome effectiveness of in use vaccines, diagnostics and antiviral drugs.

In recent years a large number of novel strains of avian influenza viruses have emerged in birds including H7N9, H5N1, H5N2, H5N3, H5N5, H5N6, H5N8, H6N1, H9N2 and H10N8. Most of these viruses can cause severe disease outbreaks in poultry and have ability to cause zoonotic infection in humans.

  • Avian influenza is a notifiable disease and should be reported

Please see the Defra website for advice on how to spot and report the disease.

Associated diseases:

AI strains can be categorised into 2 types; Highly pathogenic avian influenza (HPAI) and low pathogenicity avian influenza (LPAI).

HPAI is the more serious of the two, often being fatal in birds. Clinical signs include:

  • Swollen head
  • Blue discolouration of neck and throat
  • Loss of appetite
  • Respiratory distress such as gaping beak, coughing, sneezing, gurgling, rattling
  • Diarrhoea
  • Fewer eggs laid
  • Increased mortality

LPAI is less serious, with the severity depending on the species of bird and whether it has other infections. Clinical signs include mild breathing problems, but affected birds will not always display these signs (for example, ducks and geese can often be asymptomatic).

Disease Transmission:

The disease spreads by direct contact or through contaminated faeces and bodily fluids. New AI virus strains are created frequently which means that there is a constant risk that one of the new strains may spread easily among people. Thankfully no recent strains of AI have been proven to spread between people, only from birds to people.

Disease prevelance:

HPAI is spread across the globe, featuring mainly in North America, Asia, Europe and West Africa.

LPAI is endemic in the Middle East and South East Asia, with poultry populations being infected with strains such as H9N2. Due to the different migratory patterns of each species, it is difficult to predict where each strain will spread.

Further information and disease outbreak updates:

OIE - World Organization for Animal Health

WHO - World Health Organization

CIDRAP - Center for Infectious Disease Research and Policy

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