More Than 520 Flu Strains Going Around This Season

In its most recent (January 5) flu season summary, the Centers for Disease Control breaks down the types of influenza that are going around.

Arkansas is on the list of 47 states reporting widespread influenza activity, but is not yet on the list of states (24 total at last report, down from 29 the week before) that are reporting high flu-like illness activity.

Influenza A (H3N2), 2009 influenza A (H1N1), and influenza B viruses have all been identified in the U.S. this season. During the week ending January 5th, 3,369 of the 4,222 influenza positive tests reported to CDC were influenza A and 853 were influenza B viruses. Of the 1,586 influenza A viruses that were subtyped, 98-percent were H3 viruses and 2-percent were 2009 H1N1 viruses.

Since October 1, 2012, CDC has antigenically characterized 521 influenza viruses, including 17 2009 influenza A (H1N1) viruses, 327 influenza A (H3N2) viruses and 177 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 327 influenza A (H3N2) viruses, 325 (99-percent) 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 67-percent of the 177 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 33-percent of the tested influenza B viruses belonged to the B/Victoria lineage of viruses.

Since October 1, 2012, CDC has tested 70 2009 influenza A (H1N1), 600 influenza A (H3N2), and 230 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.

Click here for the complete flu summary from the CDC.