Explosion of H1N1 Tamiflu Resistance in Korea Continues
Recombinomics Commentary 14:05
January 14, 2009
week 50 82/95 48 3.6%
week 51 296/322 214 8.4%
week 52 767/815 471 15.39%
week 53 1275/1333 508 17.63%
The above data from the Korean CDC demonstrate the continued explosion of H1N1 Tamiflu resistance in Korea, which parallels the dramatic increase in reports of influenza like illness (ILI).
The baseline for the ILI rate is 2.6% and last season the rate peaked below 10% in week 9. This season, after crossing the baseline level in week 50, the rate jumped to 8.4% in week 51, which then jumped to 15.39% for week 52, and the latest report has the rate at 17.63%. The vast majority of influenza isolates have been H1N1. The week over week increase in H1N1 confirmations of 508 for week 52 is higher than the increase of 471 in week 53.
In the report released Friday, 16/17 H1N1 isolates were oseltamivir resistant, indicating that the vast majority of H1N1 reported in the past few weeks also has H274Y, as has been reported for neighboring Japan, as well as North America and Europe.
The explosion of H1N1 cases in Korea, in association with the fixing of H274Y is cause for concern. The sequence data from Japan and the United States identifies three receptor binding domain changes, G189V, A193T, H196R, which is likely associated with the rapid spread as well as the escape from prior immunity. None of these three changes is represented in the current H1N1 vaccine and the increased reservoir of H274Y in seasonal flu raises concerns of recombination between the N1 on H1N1 and the N1 of H5N1 to produce Tamiflu resistant H5N1. Both Korea and Japan had H5N1 in the spring of 2008, and one culler in Korea was H5 PCR confirmed.
The explosion of H1N1 in Korea may lead to similar increases in Japan and the United States. One flu outbreak has been reported at a Texas high school in the United States, where all reported influenza A has been H1N1 with H274Y.
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