What is Avian Influenza?

Avian influenza, also known as ‘avian flu’ or ‘bird flu’ is an infection- usually of wild birds- but sometimes also of commercial or domestic poultry. Water birds are the natural host of avian influenza. Avian influenza viruses are within the group of ‘influenza A viruses’ and are classified into subtypes according to two proteins found on the surface of the virus: haemagglutinin (H) and neuraminidase (N). There are 18 haemagglutinin subtypes and 11 neuraminidase subtypes. These proteins determine the kind of animal (birds, pigs, or humans) that the virus can infect.

Avian influenza and human influenza viruses are the same virus: they have the same basic viral structure, but have different H and N proteins. Human influenza is caused by ‘influenza A(H1N1)’ and ‘influenza A(H3N2)’ and influenza B. Many different avian influenza strains are responsible for bird flu outbreaks, such as ‘influenza A(H5N8)’, ‘influenza A(H5N2)’.

Rarely, avian influenza strains can cause disease in humans. Avian influenza strains that have caused disease in humans are ‘influenza A(H5N1)’ and ‘influenza A(H7N9)’