Table 1.
Influenza strain circulation among cases
| Season | % of B among all cases | B/Yamagata (%) | B/Victoria (%) | % of A among all cases | H1N1 (%) | H3N2 (%) | B strain in vaccine |
|---|---|---|---|---|---|---|---|
| 2000–2001 | 46 | 100 | 0 | 53·6 | 97 | 3 | Yamagata |
| 2001–2002 | 13 | 23 | 77 | 87·5 | 2 | 98 | Yamagata |
| 2002–2003 | 43 | 0·40 | 99·6 | 57·4 | 75 | 25 | Victoria |
| 2003–2004 | 1 | 93 | 7 | 99·0 | 0 | 100 | Victoria |
| 2004–2005 | 25 | 74 | 26 | 75·4 | 0 | 100 | Yamagata |
| 2005–2006 | 19 | 22 | 78 | 80·9 | 8 | 92 | Yamagata |
| 2006–2007 | 21 | 23 | 77 | 79·2 | 62 | 38 | Victoria |
| 2007–2008 | 29 | 98 | 2 | 71·0 | 26 | 74 | Victoria |
| 2008–2009 | 34 | 17 | 83 | 66·5 | 89 | 11 | Yamagata |
| 2009–2010 | 1 | 12 | 88 | 99·0 | 95 | 5 | Victoria |
| 2010–2011 | 26 | 6 | 94 | 74·0 | 38 | 62 | Victoria |
| 2011–2012 | 18 | 48 | 52 | 82·0 | 25 | 75 | Victoria |
| 2012–2013 | 30 | 64 | 36 | 70 | 6 | 94 | Yamagata |
Source: US Centers for Disease Control and Prevention, weekly influenza activity. http://www.cdc.gov/flu/weekly.