US flu activity decreases

Lisa Schnirring  Staff Writer

Mar 11, 2011 (CIDRAP News) – After several weeks of rising or strong flu activity, levels dropped last week, with most indicators showing declines, the US Centers for Disease Control and Prevention (CDC) said today.

The number of states reporting widespread flu activity dropped from 44 to 39 last week, and 9 reported regional activity. Some of the states reporting regional spread now are southeastern states that reported the nation's earliest widespread activity this season.

The percentage of doctor's visits for flu-like illness fell to 3.1% last week, and though it is still above the 2.5% baseline, it was lower than the 4% the CDC reported the previous week. In two of the CDC's 10 regions doctor's visits for flu-like illness fell below baseline. For the preceding few weeks, all of them had been above that level.

Nationally, the proportion of respiratory specimens that tested positive for influenza was 24.7% last week, down from 27.9% the week before. All three influenza strains are circulating. About a fourth of the isolates were influenza B. Among the subtyped influenza A strains, H3N2 had a small edge over the 2009 H1N1 virus.

The only flu indicator that rose last week was the percentage of deaths from pneumonia and influenza, which jumped from 8% to 8.5%, putting it above the epidemic threshold (8.0%) again, the CDC said. In the past the CDC has said that deaths from flu and pneumonia tend to lag other flu measures.

The CDC received five reports of pediatric flu deaths last week, raising the season's total to 60. Three were linked to influenza B, and three were associated with unsubtyped influenza A viruses. The toll of pediatric flu deaths was 14 the week before.

See also:

Mar 11 CDC flu surveillance update

Mar 11 CDC flu situation update