Commentary
H1N1
Tamiflu Resistance Clade Exchanges in Hawaii?
Recombinomics Commentary
19:02
November 28, 2008
The above comment from this week's CDC report includes information on the 19 isolates tested since the prior report, and all 19 have H274Y. The level of H274Y in clade 2B (Brisbane/59), was expected to be at or near 100% based on initial reports from Europe and Canada, as well as earlier reports from countries in the southern hemisphere where resistance was at or near 100% for the 2008 season.
However, in the United States the vast majority of H1N1 isolates were from the Pacific region and the highest levels were in Hawaii, where clade 2B and clade 2C (Hong Kong) were co-circulating last season. Last season all clade 2C isolates were amantadine resistant, but none were oseltamivir resistant (H274Y). Moreover, the level of H274Y in clade 2B was low.
Therefore, the report that all 19 of the most recent H1N1 were resistant, raises concerns that H274Y levels were increasing in clade 2C, if there were significant numbers of clade 2C isolates in the initial reports.
Recently, Hong Kong reported an increase in H274Y levels, but the 17.% reported for the 3rd quarter was far below the rate in the US and Europe which was at or near 100%. The high levels in the United State raise concerns that the high level of H274Y in clade 2B is leading to increases in co-circulating clade 2C through an exchange of genetic information, either via reaasortment or recombination
More information on clade 2C representation in the first 21 H1N1 isolates tested would be useful.
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