Widespread influenza activity has been identified in 47 states. Of the influenza strains identified across the U.S. through the week ending January 5, 2013, 80 % have been influenza A strains and 20% have been influenza B strains.
Of the circulating influenza strains that have been characterized this year, almost all (90%) have been strains predicted in this year’s seasonal flu vaccine:
This includes both influenza A strains (H1N1/California and H3 N2/Victoria). The H3N2/Victoria subtype accounts for about 98% of the influenza A strains currently circulating.
Of the influenza B strains that have been characterized this season, 67 % have been the Yamagata lineage (B/Wisconsin) predicted by this year’s seasonal flu vaccine.
The majority of currently circulating influenza viruses are susceptible to neuraminidase inhibitor antiviral medications: Oseltamivir (Tamiflu) and Zanamivir (Relenza).