This week – week 43 – shows no slow down in cases as the US enters deeper into the fall and the weather that promotes the flu.  Here is the net-net of the flu action in the US.

  • Over 99% of all subtyped influenza A viruses being reported to CDC were 2009 influenza A (H1N1) viruses.
  • The proportion of deaths attributed to pneumonia and influenza (P&I) was above the epidemic threshold.
  • 18 influenza-associated pediatric deaths were reported.
    • 15 of these deaths were associated with 2009 influenza A (H1N1) virus infection
    • 3 were associated with an influenza A virus for which the subtype was undetermined (but remember that 99% of the virus in the US is H1N1)
    • The proportion of outpatient visits for influenza-like illness (ILI) was above the national baseline. All 10 regions reported ILI above region-specific baseline levels.
    • Forty-eight states reported geographically widespread influenza activity,
      • Two states reported regional influenza activity (Hawaii and Mississippi)
      • District of Columbia reported local influenza activity
      • Puerto Rico and Guam reported sporadic influenza activity, and the U.S. Virgin Islands did not report.

Influenza-Associated Pediatric Mortality

18 Pediatric Flu Deaths This Week
  • Eighteen influenza-associated pediatric deaths were reported to CDC during week 43 (California [8] , Indiana, Louisiana [2], Mississippi, New York, Oklahoma, Texas [2], Virginia, and West Virginia).”

Outpatient Illness Surveillance:

MD visists
On a regional level, the percentage of outpatient visits for ILI ranged from 5.0% to 10.7% during week 43, and decreased (a tiny bit) in five of the 10 surveillance regions compared to the previous week. All 10 regions reported a proportion of outpatient visits for ILI above their region-specific baseline levels.

Geographic Spread of Influenza as Assessed by State and Territorial Epidemiologists:

Remember the influenza activity reported by state and territorial epidemiologists indicates geographic spread of both seasonal influenza and 2009 influenza A (H1N1) viruses and does not measure the severity of influenza activity. And 99% of the cases are H1N1.