Highly pathogenic avian influenza A virus (H5N1) has diverged an
tigenically and genetically since its initial
detection in Asia in 1997. Viruses belonging to clade 2.2 in particular hav
e been reported in numerous countries with the majority
occurring in Egypt. Previous reports identified antigenic similarities
between viruses belonging to clade 2.2. However, poultry and
human viruses isolated in northern Egypt during 2007 and 2008 were found to
be antigenically distinct from other clade 2.2 viruses
from this country. Genetic analysi