Flu season worst in a decade, H1N1 and H3N2 make appearances

Flu virus

The 2012-2013 flu season is one of the worst in 10 years, according to the Centers for Disease Control and Prevention.

The CDC said the season hasn’t yet peaked and is nevertheless running five weeks ahead of its typical yearly schedule.

Forty-one states are reporting widespread geographic influenza activity for the week of December 23-29, 2012, said the CDC on Jan. 4 --  an increase from 31 states the previous week.  The proportion of people seeing their doctors for influenza-like illness (ILI) is above the national baseline for the fourth consecutive week, climbing sharply from 2.8 percent to 5.6 percent over the past four weeks, said the health agency.

Since October 1, 2,257 laboratory-confirmed influenza-associated hospitalizations have been reported, marking an increase of 735 hospitalizations from the previous week. The numbers translate to a rate of 8.1 influenza-associated hospitalizations per 100,000 people in the U.S., it said.

The current flu season has claimed the lives of almost two dozen children, according to the CDC, with two influenza-related pediatric deaths reported during the week of December 23-29. Both deaths were associated with influenza B viruses, it said. Eighteen influenza-associated pediatric deaths occurring during the 2012-2013 season have been reported, said the CDC.

Influenza A (H3N2), 2009 influenza A (H1N1), and influenza B viruses have all been identified in the U.S. this season, it said. 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 percent were H3 viruses and two percent were 2009 H1N1 viruses. Those virus variants are all covered by the current 2012-2013 Northern Hemisphere Flu vaccine, it said.