Flu activity up but not above activity similar to past seasons

Editor's Note
Seasonal influenza activity is increasing, with the largest increases reported among children and young adults and in the northeastern and mountain west areas of the country. Nationally, the percentage of respiratory specimens testing positive for influenza, and the percentage of outpatient visits for respiratory illness and emergency department visits for influenza, and influenza-associated hospitalizations increased as of the December 4 Weekly US Influenza Surveillance Report from the CDC.

The timing of this increasing influenza activity is similar to several past seasons and no influenza-associated pediatric deaths have been reported to CDC for this season.

Influenza A(H3N2) viruses remain the most frequently reported influenza viruses so far this season at a rate of 84.3% of influenza viruses reported to public health laboratories. The CDC estimates that there have been at least 1.9 million illnesses, 19,000 hospitalizations, and 730 deaths from flu so far this season.

Among all hospitalizations for influenza, 92.9% were associated with influenza A virus, 99% were associated with influenza B virus, and 3 with influenza A virus and influenza B virus co-infection, and 0.2% with influenza virus for which the type was not determined. Among those with influenza A subtype information, 79.3% were A(H3N2), and 20.7% were A(H1N1).