Recombinomics Commentary January 30, 2009
The rapidly increasing number of patients, and Japan is still calling for wearing masks. the number of flu patients has doubled in the last week
Diseases Control Division, said County, this winter, took measures to close down schools and school classes let out by a group of influenza infection (primary and middle school, high school, kindergarten, nursery school), total up to 151 school gardens
The above translations are from influenza alerts issued across Japan this week because of the dramatic jump in cases. These alerts correlate with a recent increase in H1N1 isolates reported by Japan to FluNet, suggesting much of the increase is due to Tamiflu resistant infections. Earlier this season there were outbreaks in primary schools in a few prefectures, and these outbreaks were due to H1N1 that was Tamiflu resistant and closely related to H1N1 isolates in the United States this season.
Although these isolates are clade 2B and related to the H1N1 vaccine target, Brisbane/59, they have evolved away from the 2007 isolate, and reports from Italy indicate patients are H1N1 infected even though they had been vaccinated this season. In the United States H1N1 is dominant and H274Y was been confirmed in 162/165 isolates collected from 26 states. Similar frequencies have been described for Europe and Canada.
In neighboring Korea, H1N1 have exploded in recent weeks. Over 400 isolates have been reported for each week this year, raising concerns that the H1N1 has expanded rapidly in recent weeks, is resistant to Tamiflu and the current trivalent vaccine directed against Brisbane/59.
The resistance is likely linked to A193T, which is present in all public sequences from the United States this season (HI, TX, PA, WI). Phylogenetic analysis of HA and NA in Japan indicates A193T is likely in at least 31/33 sequenced H1N1 isolates.
The emergence of H1N1 that is resistant to Tamiflu as well as the trivalent vaccine increases the likelihood of a dual infection involving H1N1 and H5N1 leading to the emergence of H5N1 with H274Y.