Tuesday, November 20, 2012

Researchers say H5N1 viruses in Egypt may pose special pandemic risk

[editing is mine]
November 19, 2012
Most H5N1 avian influenza viruses in Egypt have two mutations that may make them more transmissible in mammals, thus posing a greater threat of sparking a human pandemic than H5N1 viruses elsewhere, according to experts whose research on H5N1 transmissibility sparked a major controversy in the past year. The finding was reported by Ron Fouchier, PhD, Yoshihiro Kawaoka, DVM, PhD, and three other authors in an opinion article published last week in PLoS Pathogens. Their conclusion was based on an inspection of publicly available hemagglutinin (HA) sequences from H5N1 viruses. Fouchier led a team that showed that as few as five mutations could give H5N1 viruses airborne transmissibility in ferrets, and Kawaoka's team showed that a hybrid virus containing H5 HA, with certain mutations, also could be an airborne spreader in ferrets. The studies were published in May and June after a long debate in science and government circles about whether the details should be released. The studies revealed, among other things, that a mutation involving loss of a glycosylation site at HA positions 154-156 appears to be critical for H5 virus transmission in mammals, according to the PLoS Pathogens article. When the team examined available HA sequences from avian H5N1 viruses, they found that more than 70% of Egyptian isolates lacked the HA 154-156 glycosylation site, versus about 25% of isolates from Vietnam and none from Indonesia. An analysis of human isolates from the three countries revealed a similar pattern. In addition, the researchers say the mutation PB2-627K, which is known to be involved in mammalian adaptation of avian flu viruses, is found in most H5N1 isolates from Egypt.
Nov 15 PLoS Pathogens article


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