Commentary
Tamiflu Resistant H1N1 Explodes in Japan
Recombinomics Commentary 18:10
February 2, 2009
The above may be true for the beginning of the season in the United States, but reports coming out of Korea and Japan indicate major changes will be noticed I the US in the next few weeks.
Last month H1N1 exploded on South Korea, where almost all influenza this season is Tamiflu resistant H1N1. The high level of activity was reported for the entire month, with more than 400 isolates collected each week.
Similarly, H1N1 exploded last week in Japan. The jump in cases led to school closings across the country, with warnings to stay away from crowds and wear masks. The warnings were based on the number of patients per reporting location to rise above 30 (see updated map), which was widespread and included Tokyo, where 136 elementary and 36 middle schools were closed last week.
Earlier in the season H1N1 accounted for 1/3 of flu cases in Japan, but last week’s activity moved the number above 54.6% indicating much of the increase was due to Tamiflu resistant H1N1. Moreover, a recent report from the Japan NIH indicated the H1N1 was rapidly losing effectiveness, with ferret titers 4-8 fold lower than the Brisbane/59 used as the vaccine target, and in some samples the activity was close to the lower limit of detection.
The phylogenetic analysis of H1N1 closing schools in Japan in the fall was similar to the H1N1 in the United States, so it is likely that the explosion in cases in Korea and Japan will soon be in the United States. There have already been reports of school closings or alerts in Texas, where Tamiflu resistance is widespread and the sequences from Texas were similar to Japan as well as HI, PA, and WI in the US. Moreover, the H1N1 in Italy is also developing vaccine resistance.
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