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North America Flu Surveillance Week 8

 


# 5356

 

 

Influenza activity across the United States remains elevated, while in Canada it is more of a mixed bag – with parts of Quebec and BC seeing increases while other regions are seeing a decline.

In the US, 14 pediatric deaths were reported, although only 4 of those appeared to have occurred during week 8. 

 

Other major indicators include the nation’s P&I (pneumonia & influenza) mortality numbers dropped again this week to 8%, which is right at the epidemic threshold for this week -  and ILI consultations dropped to 4%, but still remain well above the national baseline of 2.5%.

 

 

First up, the FluWatch report from Canada, followed by the US’s FluView.  Follow the links to read them in their entirety.

 

 

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Summary of FluWatch Findings for the Week ending February 26, 2011

  • In week 08, regions in Quebec and BC reported increases in influenza activity, while other regions across the country reported decreased activity. Many school outbreaks of ILI continue to be reported in New Brunswick. The proportion of positive influenza detections overall continued to decline in week 08, although the ILI consultation rate increased slightly compared to the previous week.
  • Since the beginning of the season, 86.1% of the subtyped positive influenza A specimens have been influenza A/H3N2. In week 08, pandemic H1N1 2009 detections decreased to 7% of positive influenza detections while the proportion of influenza B detections increased to 12%.

 

Percent positive influenza tests, compared to other respiratory viruses, Canada, by reporting week, 2010-2011

Percent positive influenza tests, compared to other respiratory viruses, Canada, by reporting week, 2010-2011

 

 

 

From the CDC, this week’s FluView Report.

 

2010-2011 Influenza Season Week 8 ending February 26, 2011

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Synopsis:

During week 8 (February 20-26, 2011), influenza activity in the United States remained elevated.

  • Of the 7,543 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, 2,106 (27.9%) were positive for influenza.
  • The proportion of deaths attributed to pneumonia and influenza (P&I) was at the epidemic threshold.
  • Fourteen influenza-associated pediatric deaths were reported bringing the season total to 55. Four of these deaths were associated with an influenza B virus, four were associated with a 2009 influenza A (H1N1) virus, two were associated with an influenza A (H3) virus, and four were associated with an influenza A virus for which the subtype was not determined.
  • The proportion of outpatient visits for influenza-like illness (ILI) was 4.0%, which is above the national baseline of 2.5%. All 10 regions reported ILI above region-specific baseline levels. Eighteen states experienced high ILI activity; six states experienced moderate ILI activity; New York City and 16 states experienced low ILI activity; 10 states experienced minimal ILI activity, and the District of Columbia had insufficient data.
  • The geographic spread of influenza in 44 states was reported as widespread; five states reported regional influenza activity; the District of Columbia and one state reported local influenza activity; Puerto Rico and the U.S. Virgin Islands reported sporadic influenza activity, and Guam reported no influenza

U.S. Virologic Surveillance:

WHO and NREVSS collaborating laboratories located in all 50 states and Washington D.C. report to CDC the number of respiratory specimens tested for influenza and the number positive by influenza type and subtype. The results of tests performed during the current week are summarized in the table below.

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Antigenic Characterization:

CDC has antigenically characterized 1,004 influenza viruses [160 2009 influenza A (H1N1) viruses, 488 influenza A (H3N2) viruses, and 356 influenza B viruses] collected by U.S. laboratories since October 1, 2010.

    2009 Influenza A (H1N1) [160]

  • One hundred fifty-nine (99.4%) of the 160 tested were characterized as A/California/7/2009-like, the influenza A (H1N1) component of the 2010-11 influenza vaccine for the Northern Hemisphere. One virus (0.6%) of the 160 tested showed reduced titers with antiserum produced against A/California/7/2009.

    Influenza A (H3N2) [488]

  • Four hundred eighty-three (99.0%) of the 488 tested were characterized as A/Perth/16/2009-like, the influenza A (H3N2) component of the 2010-11 influenza vaccine for the Northern Hemisphere. Five viruses (1.0%) of the 488 tested showed reduced titers with antiserum produced against A/Perth/16/2009.

    Influenza B (B/Victoria/02/87 and B/Yamagata/16/88 lineages) [356]
    Victoria Lineage [338]

  • Three hundred thirty-eight (94.9%) of the 356 influenza B viruses tested belong to the B/Victoria lineage of viruses.
    • Three hundred thirty-seven (99.7%) of these 338 viruses were characterized as B/Brisbane/60/2008-like, the recommended influenza B component for the 2010-11 Northern Hemisphere influenza vaccine.
    • One (0.3%) of these 338 viruses showed somewhat reduced titers with antisera produced against B/Brisbane/60/2008.

    Yamagata Lineage [18]

  • Eighteen (5.1%) of the 356 viruses were identified as belonging to the B/Yamagata lineage of viruses.

Influenza-Associated Pediatric Mortality

Fourteen influenza-associated pediatric deaths were reported to CDC during week 8. Four of these deaths were associated with an influenza B virus, four were associated with a 2009 influenza A (H1N1) virus, two were associated with an influenza A (H3) virus, and four were associated with an influenza A virus for which the subtype was not determined.

Fifty-five deaths from 25 states (Arizona, Colorado, Florida, Georgia, Hawaii, Illinois, Indiana, Kentucky, Louisiana, Michigan, Minnesota, Nevada, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Pennsylvania, Texas, Utah, Virginia, West Virginia, and Wisconsin) and New York City have been reported during this influenza season. Twenty of the 55 deaths reported were associated with influenza B viruses, 12 deaths reported were associated with influenza A (H3) viruses, 12 were associated with 2009 influenza A (H1N1) viruses, and 11 were associated with an influenza A virus for which the subtype was not determined.

Influenza-Associated Pediatric Mortality

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