Table 2.
Distribution of Circulating Influenza Viruses and Predominant Influenza A Subtype, by Season, United States, 2000–2001 to 2016–2017
| Season | Period | Predominant Influenza A Virus Subtype |
Percentage of Circulating Viruses |
||
|---|---|---|---|---|---|
| H1 | H3 | B | |||
| Prepandemic | |||||
| 2000–2001 | A/H1 | 52% | 2% | 47% | |
| 2001–2002 | A/H3 | 2% | 84% | 14% | |
| 2002–2003 | A/H1 | 41% | 17% | 42% | |
| 2003–2004 | A/H3 | 0% | 99% | 1% | |
| 2004–2005 | A/H3 | 0% | 75% | 25% | |
| 2005–2006 | A/H3 | 8% | 72% | 21% | |
| 2006–2007 | A/H1 | 49% | 30% | 21% | |
| 2007–2008 | A/H3 | 18% | 53% | 29% | |
| 2008–2009 | A/H1 | 58% | 8% | 34% | |
| Pandemic and Later | |||||
| 2009–2010 | A/H1pdm09 | 95% | 4% | 1% | |
| 2010–2011 | A/H3 | 28% | 46% | 26% | |
| 2011–2012 | A/H3 | 21% | 60% | 18% | |
| 2012–2013 | A/H3 | 4% | 66% | 30% | |
| 2013–2014 | A/H1pdm09 | 74% | 11% | 15% | |
| 2014–2015 | A/H3 | 0% | 83% | 17% | |
| 2015–2016 | A/H1pdm09 | 56% | 14% | 30% | |
| 2016–2017 | A/H3 | 2% | 75% | 23% | |