Avian Influenza (H5N1) and its Pandemic Potential

Avian influenza or bird flu, a highly contagious, transboundary, viral respiratory disease of birds and sporadically infecting humans. The disease is caused by Avian Influenza type A Virus (AIV), belonging to the family Orthomyxoviridae. These are enveloped, single-stranded, negative sense RNA viruses with segmented genome (8 segments), coding for 12 major proteins. The virus sub-typing is done based on the two important viral surface glycoproteins such as Hemagglutinin (HA) and Neuraminidase (NA). The HA is involved in virus entry into the cell and NA in its release from the cell, thus playing an important role in influenza virus replication cycle. Till date, 16 HA and 9NA subtypes have been detected in birds, thus AIV can reemerge into 144 possible combinations [1]. Wild Aquatic birds act as natural reservoirs of influenza virus worldwide and the main source of infection to domestic poultry.