H1N1 Tamiflu Resistance in Hong Kong Approaches 100%
Recombinomics Commentary 09:59
January 23, 2009
Presence of mutation for oseltamivir resistance (H274Y): 72/80 (90%)
The above comments are from the quarterly report on influenza isolates in Hong Kong. If none of the above isolates have NA H274Y and M2 S31N, then it is likely that 73/80 isolates are clade 2B (with H274Y in 72/73) and the remaining seven are clade 2C (which had S31N at levels close to 100% last season). The report covers the last quarter of the 2008 calendar year, and it is likely that clade 2B levels are now near 100%. as reported for South Korea, Japan, and Taiwan. Moreover, most of the influenza in Hong Kong is H1N1 as described in the week 2 report.
Thus, it is increasingly likely that the levels of H274Y in H1N1 in China and Russia are also near 100%, as was seen in Europe and North America.
The worldwide fixing of H274Y in H1N1 has significant pandemic implications. The fixing of H274Y is due to hitch hiking onto a sub-clade of 2B that had acquired key changes via homologous recombination. Moreover, there are markers that trace the origins back to northern Vietnam, raising concerns that the H274Y in H1N1 was due to H274Y in H5N1, which was associated with use of Tamiflu blankets to control the spread of H5N1 in confirmed and suspect patients and contacts.
The H1N1 acquisition of H274Y from H5N1 raises concerns that the fixing of H274Y in H1N1 will lead to widespread H274Y in H5N1 in countries where both subtypes are circulating such as China. The spread of H5N1 has been largely controlled by the liberal use of oseltamivir, and resistance in evolutionarily fit H5N1 would be catastrophic.
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