الفهرس 
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Abstract
In the present study 11 H5N1 viruses form 2010 to 2015 were molecularly characterized. Phylogenic analysis for four genes of these viruses gave genetic prospective of the viruses circulating in Egypt and identifying specific mutations associated with enhancing replication and virulence in mammalian species. This study indicate that the highly pathogenic avian influenza viruses circulating in Egypt during the period from 2010 to 2015 are belonging to clade 2.2.1.2 and its new cluster from2.2.1.2/2015 and old clade 2.2.1.1. All viruses showed presence of multiple basic amino acids at the HA cleavage site which is considered the primary virulence factor in addition to a lysine residue at amino acid 627 in PB2 gene that has been found to influence the virulence in mice and humans.
It was found that PB1 gene in all our viruses of sub clade 2.2.1.2 contain T182I, K214R and L384S while our variant strain of sub clade 2.2.1.1 contains N642S, R584 H and R430K mutation, two mutations were recorded in NP gene of Egyptian viruses seem to be human-associated as V33I that is present in 3 viruses , besides, I109V that is present in all our classical viruses but not in variant virus.