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2009-2010 Influenza Season Week 43 ending October 31, 2009

During week 43 (October 25-31, 2009), influenza activity remained elevated in the U.S.

  • 5,258 (37.2%) specimens tested by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories and reported to CDC/Influenza Division were positive for influenza.
  • 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.
  • Eighteen influenza-associated pediatric deaths were reported. Fifteen of these deaths were associated with 2009 influenza A (H1N1) virus infection and three were associated with an influenza A virus for which the subtype was undetermined.
  • 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, the District of Columbia reported local influenza activity; Puerto Rico and Guam reported sporadic influenza activity, and the U.S. Virgin Islands did not report.

3 Responses to “2009-2010 Influenza Season Week 43 ending October 31, 2009”

  • James says:

    Pneumonia and Influenza Hospitalization and Death Tracking:

    This new system was implemented on August 30, 2009, and replaces the weekly report of laboratory confirmed 2009 H1N1-related hospitalizations and deaths that began in April 2009. Jurisdictions can now report to CDC counts of hospitalizations and deaths resulting from all types or subtypes of influenza, not just those from 2009 H1N1 influenza virus.

    To allow jurisdictions to implement the new case definition, counts were reset to zero on August 30, 2009. From August 30 – October 31, 2009, 17,838 laboratory-confirmed influenza associated hospitalizations and 672 laboratory-confirmed influenza associated deaths were reported to CDC. CDC will continue to use its traditional surveillance systems to track the progress of the 2009-10 influenza season.

  • Honead says:

    Antigenic Characterization:

    CDC has antigenically characterized one seasonal A (H1N1), two A (H3N2) and 239 2009 influenza A (H1N1) viruses collected since September 1, 2009.

    One seasonal influenza A (H1N1) viruses was tested and is related to the influenza A (H1N1) component of the 2009-10 Northern Hemisphere influenza vaccine (A/Brisbane/59/2007).

    Both influenza A (H3N2) viruses tested showed reduced titers with antisera produced against A/Brisbane/10/2007, the 2009-2010 Northern Hemisphere influenza A (H3N2) vaccine component, and were antigenically related to A/Perth/16/2009, the WHO recommended influenza A (H3N2) component of the 2010 Southern Hemisphere vaccine formulation.

    Two hundred thirty-eight (99.6%) of 239 2009 influenza A (H1N1) viruses tested are related to the A/California/07/2009 (H1N1) reference virus selected by WHO as the 2009 H1N1 vaccine virus and one virus (0.4%) tested showed reduced titers with antisera produced against A/California/07/2009.

    Annual influenza vaccination is expected to provide the best protection against those virus strains that are related to the vaccine strains, but limited to no protection may be expected when the vaccine and circulating virus strains are so differenct as to be from different lineages. Antigenic characterization of 2009 influenza A(H1N1) viruses indicates that these viruses are only distantly related antigenically and genetically to seasonal influenza A(H1N1) viruses, suggesting that little to no protection would be expected from vaccination with seasonal influenza vaccine.

    It is too early in the influenza season to determine if seasonal influenza viruses will circulate widely or how well the vaccine and circulating strains will match.

  • Jan says:

    Influenza-Associated Pediatric Mortality

    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). Fifteen of these deaths were associated with 2009 influenza A (H1N1) virus infection and three were associated with an influenza A virus for which the subtype is undetermined.

    These deaths occurred between July 12 and October 31, 2009. Seven deaths reported during week 43 occurred during the 2008-09 season, bringing the total number of reported pediatric deaths occurring during that season to 124. Since August 30, 2009, CDC has received 85 reports of influenza-associated pediatric deaths that occurred during the current influenza season (12 deaths in children less than 2 years old, nine deaths in children 2-4 years old, 30 deaths in children 5-11 years old, and 34 deaths in individuals 12-17 years old).

    Seventy-three of the 85 deaths were due to 2009 influenza A (H1N1) virus infections, and the remaining 12 were associated with influenza A virus for which the subtype is undetermined. A total of 129 deaths in children associated with 2009 influenza A (H1N1) virus infection have been reported to CDC.

    Among the 85 deaths in children, 53 children had specimens collected for bacterial culture from normally sterile sites and 17 (32.1%) of the 53 were positive; Staphylococcus aureus was identified in eight (47.1%) of the 17 children. One S. aureus isolate was sensitive to methicillin, six were methicillin resistant, and one did not have sensitivity testing performed. Twelve (70.6%) of the 17 children with bacterial coinfections were five years of age or older, and five (29.4%) of the 17 children were 12 years of age or older.

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