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From the beginning of the 2010/11 season, the number of reports of detection/isolation of AH3 exceeded that of AH1pdm. After week 49 of 2010, the number of detection/isolation of AH1pdm increased and decreased after the peak at week 3 of 2011. From week 7 of 2011, the number of reports of detection/isolation of AH3 exceeded that of AH1pdm again. From week 12 of 2011, the number of reports of detection/isolation of type B exceeded that of type A (Fig. 1).
From week 36 of 2010 (the first week of the 2010/11 season) to week 19 of 2011, isolation/detection of AH1pdm from 6,244 cases in all 47 prefectures, AH3 from 3,769 cases in all prefectures, B/Victoria lineage from 1,327 cases in 44 prefectures, B/Yamagata lineage from 33 cases in 13 prefectures and B/lineage not determined from 351 case in 32 prefectures were reported (Fig. 2).
The proportion of AH1pdm (6,244 cases) to all influenza virus (11,724 cases) is 53% (AH3 32% and B 15%).
Of 11,724 cases, 60 were imported cases (33 of AH1pdm, 22 of AH3 and 5 of B).
[Reference figure] Weekly cases of influenza and isolation/detection of influenza viruses from week 36 of 2008 to week 19 of 2010
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Isolation/detection of influenza virus in Japan, from week 19 (May 4-10) of 2009 to week 19 (May 10-16) of 2010 (as of May 13, 2010)
