Avian/Bird influenza is a disease affecting birds that is caused by several types of Influenza viruses.

Highly Pathogenic Avian Influenza (HPAI) is a highly contagious disease affecting wild birds and poultry, and has been responsible for recent human outbreaks and deaths in Asian countries.

There are three types of influenza viruses - A, B and C. Only types A and B cause significant human disease.

Influenza A is further sub-typed according to the type of haemagglutinin (H) and neuraminidase (N) proteins on its outer layer.

There are 15 different H types (H1, H2, H3, etc) and 9 different N types (N1, N2, N3, etc).