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Tamflu Resistance Near 100% In Japan
Among A(H1N1) viruses tested, 13 of 14 in the United Kingdom,1 of 1 in Israel, 1 of 1 in Ghana and 1 of 1 in Canada had the specific neuraminidase mutation (H275Y; numbered according to N1 sequence) associated with oseltamivir resistance.
Japan also reported that 13 of 14 A(H1N1) viruses tested were resistant.
The above comments are from the December 30, 2008 WHO report on oseltamivir resistance (H274Y in the northern hemisphere. The number of samples tested is low, because the report covers a very small time period at teh begiing of the flu season. Data from the UK has been updated at the UK website to 29/30. The only sensitive isolate was from the very beginning of the season. The same was true in the United States. The one sensitive sample was reported with one resistant sample in the first report. After that, the next 69 isolates had H274Y.
The same sequence of events will probably hold for Japan. As additional samples are collected, the frequency will approach 100%. The figures for Japan are somewhat surprising since last season there was a significant level of clade 2C (Hong Kong), which was oseltamivir sensitive. The same was true for Hawaii in the United States, but this season all reported H1N1 tests have had H274Y in Hawaii, suggesting clade 2B had gain dominance over clade 2C.
The data above for Japan indicates the same dominance had happened there, suggesting the frequency of almost 100% in Europe and North America extends to other northern countries in Asia, like Japan, China, and Russia.
Therefore, it seems likely that clade 2C may have been displaced throughout the northern hemisphere by clade 2B, which is now represented by a dominant sub-clade that has acquired and fixed H274Y.