Background:
In the last decade H9N2 avian influenza viruses had caused outbreaks in poultry in many parts of the world. This subtype could infect other animals such as human and pig. Avian H9N2 virus has acquired receptor binding characteristics typical of humans strains, increasing the potential for reassortment in both human and pig respiratory tracts. This indicates that the A/H9N2 would be a potential threat to human population.