الفهرس 
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Abstract
Avian influenza virus (AIV) is one of most important viral diseases that has different waves of infection and development because of the nature of its genetic structure where the amino acid of AIV consists of 8 segments of RNA that leads to antigenic shift and antigenic drift. So that, the isolation of the circulating strains should be applied regularly.
It has emerged in recent years that the name influenza comes from the Italian: influenza, meaning ”influence”, (Latin: influentia), AIV related to Family Orthomyxoviridae, Genus Influenza viruses A, Type Avian influenza A virus(AIV).
AIV is pleiomorphic with a size ranging from 80–120nm, enveloped and has a genome that consists of eight negative sense single stranded RNA segments that encode ten proteins. AIV is classified by the two surface antigens it carries in the envelope, heamagglutinin (HA) and neuraminidase (NA), there were 16 HA subtypes (H1-H16) and 9 NA subtypes (N1-N9) had been identified , but recently H17N10 and H18N11 which are maintained in aquatic birds and bats respectively.
There are different strains of AIV as it is divided in to low pathogenic (LPAIV) or high pathogenic (HPAIV). The geographical distribution of AIV covers worldwide and the HPAIV belonging to the H5N1 subtype are endemic in Asia and are spreading in Europe and Africa including Egypt.
Occasionally other strains such as H5N1, H7N7, H9N2 and recently H7N9 have been isolated from human, although these strains display limited spread among humans.
The main reservoir of influenza A is aquatic birds, but virus has a broad host tropism and also infects humans and other mammals. In contrast to the widespread infectivity in birds, only three influenza A strains have been fully adapted to humans the last century.