cdc.gov
- Influenza A (H3N2), 2009 influenza A (H1N1), and influenza B viruses have all been identified in the U.S. this season. During the week of December 23-29, 2,346 of the 2,961 influenza positive tests reported to CDC were influenza A and 615 were influenza B viruses. Of the 1,234 influenza A viruses that were subtyped, 98% were H3 viruses and 2% were 2009 H1N1 viruses.
- Since October 1, 2012, CDC has antigenically characterized 413 influenza viruses, including 17 2009 influenza A (H1N1) viruses, 281 influenza A (H3N2) viruses and 115 influenza B viruses.
------ All 17 of the 2009 influenza A (H1N1) viruses were characterized as A/California/7/2009-like. This is the influenza A (H1N1) component of the Northern Hemisphere vaccine for the 2012-2013 season.
------ Of the 281 influenza A (H3N2) viruses, 279 (99%) were characterized as A/Victoria/361/2011-like. This is the influenza A (H3N2) component of the Northern Hemisphere influenza vaccine for the 2012-2013 season.
----- Approximately 69% of the 115 influenza B viruses belonged to the B/Yamagata lineage of viruses, and were characterized as B/Wisconsin/1/2010-like, the influenza B component for the 2012-2013 Northern Hemisphere influenza vaccine. The remaining 31% of the tested influenza B viruses belonged to the B/Victoria lineage of viruses.
- Since October 1, 2012, CDC has tested 39 2009 influenza A (H1N1), 526 influenza A (H3N2), and 226 influenza B virus isolates for resistance to neuraminidase inhibitors this season. The tested viruses showed susceptibility to the antiviral drugs oseltamivir and zanamivir. High levels of resistance to the adamantanes (amantadine and rimantadine) persist among 2009 influenza A (H1N1) and A (H3N2) viruses. Adamantanes are not effective against influenza B viruses. |
