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NAMRU-3 has recently released HA and NA sequences from recent H5N1 cases in Egypt (11 from 2009 and 12 from 2010). All 23 HA sequences had 133del (3 BP deletion using H3 numbering), indicating the deletion is becoming fixed in human H5N1 in Egypt. An earlier paper, “Characterization of conserved properties of hemagglutinin of H5N1 and human influenza viruses: possible consequences for therapy and infection control” had noted similarities between H5N1and seasonal H1N1, raising concerns of increased human transmission (H2H) of H5N1 with 133del. This concern was increased by the recent paper describing the detection of H5N1 in donkeys and serological evidence of widespread H5N1 antibodies in donkeys.
Concerns of human to human H5N1 transmission in Egypt were raised when mild cases in children were reported in the spring of 2007. Several had the 3 BP deletion and sequences were closely related. There children had a mild course, which did not include pneumonia.
In early 2009, mild cases were reported in toddlers. The large number of cases reduced the case fatality rate for H5N1 in 2009 to approximately 10%. The sequences from these toddlers also had 133del, which was followed by the most recent 23 sequences which were from the summer of 2009 to March 31, 2010.
Poultry H5N1 sequences collected in the past year were more diverse and included vaccine resistant H5N1. However, all human sequences contained 133del and many of the 2010 sequences were closely related to each other raising additional concerns that H5N1 is transmitting H2H.
Since Egypt does not H5N1 test patients who do not have a poultry contact, the full extent of H5N1 remains largely unknown. Serological testing has been discussed for over a year. During that time a serological survey on donkeys was conducted, which showed widespread antibodies in donkey serum.
Results for a comparable test in humans, using a 133del H5N1 target is long overdue.