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Student Health Services

Flu Activity in the United States

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).
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