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    Weekly Report: Influenza Summary Update

    2007-2008 Influenza Season Week 45, ending November 10, 2007

    The report for week 46 (ending November 17, 2007) will be posted on Monday, Nov. 26, 2007

    (All data are preliminary and may change as more reports are received.)

    Synopsis

    During week 45 (November 4-10, 2007), a low level of influenza activity was reported in the United States.

    • Forty-eight (2.7%) specimens tested by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories were positive for influenza.
    • The proportion of deaths attributed to pneumonia and influenza was below the epidemic threshold.
    • The proportion of outpatient visits for influenza-like illness (ILI) and acute respiratory illness (ARI) was below national baseline levels. The Mountain and New England regions reported ILI slightly above their region-specific baselines.
    • Three states reported local activity; 21 states and the District of Columbia reported sporadic influenza activity; and 26 states reported no influenza activity.

    National and Regional Summary of Select Surveillance Components

    Region
    Data for current week Data cumulative for the season
    Sentinel Provider ILI* DoD and VA ARI* % pos. for flu† # jurisdictions reporting regional or widespread activity‡ A (H1) A (H3) A Unsub-typed B Pediatric Deaths
    Nation Normal Normal 2.7% 0 of 51 41 7 182 18 0
    New England Elevated Normal 0.7% 0 of 6 2 0 2 2 0
    Mid-Atlantic Normal Normal 0.2% 0 of 3 2 0 0 0 0
    East North Central Normal Normal 0.8% 0 of 5 0 0 0 2 0
    West North Central Normal Normal 0.3% 0 of 7 2 0 4 1 0
    South Atlantic Normal Normal 3.6% 0 of 9 0 2 82 6 0
    East South Central Normal Normal 0.3% 0 of 4 1 0 0 0 0
    West South Central Normal Normal 3.9% 0 of 4 1 4 72 1 0
    Mountain Elevated Normal 1.8% 0 of 8 9 0 4 3 0
    Pacific Normal Normal 2.8% 0 of 5 24 1 18 3 0

    * Elevated means the % of visits for ILI or ARI is at or above the national or region-specific baseline
    † National data is for current week; regional data is for the most recent 3 weeks.
    ‡ Includes all 50 states and the District of Columbia

    Laboratory Surveillance

    During week 45, WHO and NREVSS laboratories reported 1,811 specimens tested for influenza viruses, 48 (2.7%) of which were positive, including three influenza A (H1) viruses (Mountain region), one influenza A (H3) virus (West South Central region), 40 influenza A viruses that were not subtyped (Mountain, New England, South Atlantic, and West South Central regions) and four influenza B viruses (New England and South Atlantic regions). The District of Columbia and 22 states from all nine surveillance regions have reported laboratory confirmed influenza this season with Florida, Hawaii, and Texas accounting for 195 (78.6%) of the 248 reported influenza viruses.

    INFLUENZA Virus Isolated
    View WHO-NREVSS Regional Bar Charts | View Chart Data | View Full Screen

    Antigenic Characterization:

    CDC has antigenically characterized one influenza virus collected by U.S. laboratories since September 30, 2007. The influenza B virus was characterized as B/Florida/04/2006, belonging to the B/Yamagata lineage. Influenza B viruses currently circulating can be divided into two antigenically distinct lineages represented by the B/Yamagata/16/88 and B/Victoria/02/87 viruses. The recommended influenza B component for the 2007-08 influenza vaccine is B/Malaysia/2506/2004-like viruses, belonging to the B/Victoria lineage.

    Pneumonia and Influenza (P&I) Mortality Surveillance:

    During week 45, 5.8% of all deaths reported through the 122-Cities Mortality Reporting System were reported as due to P&I. This percentage is below the epidemic threshold of 6.1% for week 45.

    Pneumonia And Influenza Mortality
    View Full Screen

    Influenza-Associated Pediatric Mortality

    Two influenza-associated pediatric deaths were reported during week 45 from Texas. These two deaths occurred during the 2006-07 season bringing the total number of cases occurring during that season to 73. No deaths have been reported for the 2007-08 season.

    Influenza-Associated Pediatric Mortality
    View Full Screen

    Influenza-Associated Pediatric Hospitalizations

    Laboratory-confirmed influenza-associated pediatric hospitalizations are monitored in two population-based surveillance networks: the Emerging Infections Program (EIP) and the New Vaccine Surveillance Network (NVSN). No influenza-associated pediatric hospitalizations have been reported from the EIP. NVSN estimated rates of hospitalization for influenza will be reported every two weeks, beginning November 30, 2007.

    Outpatient Illness Surveillance

    Nationwide during week 45, 1.6% of patient visits reported through the U.S. Influenza Sentinel Provider Surveillance Network were due to influenza-like illness (ILI) and 2.1% of patient visits to Department of Veteran’s Affairs (VA) and Department of Defense (DoD) outpatient treatment facilities were for acute respiratory illness (ARI). These percentages are less than the national baselines of 2.2% and 3.2%, respectively. On a regional level, the percentage of visits for ILI ranged from 0.9% to 3.7% and the percentage of visits for ARI ranged from 1.0% to 2.5%. The Mountain and New England regions reported ILI above their region-specific baselines. All nine regions reported percentages of visits for ARI below their respective region-specific baselines. All five age groups reported percentages of visits for ARI below their respective age-specific baselines.

    national levels of ILI and ARI
    View Sentinel Providers Regional Charts | View Chart Data |View Full Screen
    Bar Chart for Influenza-like Illness
    View Full Screen

    Geographic Spread of Influenza as Assessed by State and Territorial Epidemiologists

    Influenza activity was reported as local in three states (Florida, Hawaii, and Louisiana) and as sporadic in 21 states (Alaska, California, Colorado, Connecticut, Delaware, Idaho, Indiana, Kentucky, Massachusetts, Minnesota, Mississippi, Nevada, New Jersey, New York, Oklahoma, Oregon, Pennsylvania, South Dakota, Tennessee, Texas, and Utah) and the District of Columbia. Twenty-six states reported no influenza activity.

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    A description of surveillance methods is available at: http://www.cdc.gov/flu/weekly/fluactivity.htm

    • Page last updated November 16, 2007
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