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Epidemiology of influenza in West Africa after the 2009 influenza A(H1N1) pandemic, 2010-2012

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  • Epidemiology of influenza in West Africa after the 2009 influenza A(H1N1) pandemic, 2010-2012

    BMC Infect Dis. 2017 Dec 4;17(1):745. doi: 10.1186/s12879-017-2839-1.
    Epidemiology of influenza in West Africa after the 2009 influenza A(H1N1) pandemic, 2010-2012.

    Talla Nzussouo N1,2,3, Duque J4,5, Adedeji AA6, Coulibaly D7, Sow S8, Tarnagda Z9, Maman I10, Lagare A11, Makaya S12, Elkory MB13, Kadjo Adje H14, Shilo PA6, Tamboura B8, Cisse A9, Badziklou K10, Ma´nassara HB11, Bara AO13, Keita AM8, Williams T4, Moen A4, Widdowson MA4, McMorrow M4,15.
    Author information

    Abstract

    BACKGROUND:

    Over the last decade, capacity for influenza surveillance and research in West Africa has strengthened. Data from these surveillance systems showed influenza A(H1N1)pdm09 circulated in West Africa later than in other regions of the continent.
    METHODS:

    We contacted 11 West African countries to collect information about their influenza surveillance systems (number of sites, type of surveillance, sampling strategy, populations sampled, case definitions used, number of specimens collected and number of specimens positive for influenza viruses) for the time period January 2010 through December 2012.
    RESULTS:

    Of the 11 countries contacted, 8 responded: Burkina Faso, Cote d'Ivoire, Mali, Mauritania, Niger, Nigeria, Sierra Leone and Togo. Countries used standard World Health Organization (WHO) case definitions for influenza-like illness (ILI) and severe acute respiratory illness (SARI) or slight variations thereof. There were 70 surveillance sites: 26 SARI and 44 ILI. Seven countries conducted SARI surveillance and collected 3114 specimens of which 209 (7%) were positive for influenza viruses. Among influenza-positive SARI patients, 132 (63%) were influenza A [68 influenza A(H1N1)pdm09, 64 influenza A(H3N2)] and 77 (37%) were influenza B. All eight countries conducted ILI surveillance and collected 20,375 specimens, of which 2278 (11%) were positive for influenza viruses. Among influenza-positive ILI patients, 1431 (63%) were influenza A [820 influenza A(H1N1)pdm09, 611 influenza A(H3N2)] and 847 (37%) were influenza B. A majority of SARI and ILI case-patients who tested positive for influenza (72% SARI and 59% ILI) were children aged 0-4 years, as were a majority of those enrolled in surveillance. The seasonality of influenza and the predominant influenza type or subtype varied by country and year.
    CONCLUSIONS:

    Influenza A(H1N1)pdm09 continued to circulate in West Africa along with influenza A(H3N2) and influenza B during 2010-2012. Although ILI surveillance systems produced a robust number of samples during the study period, more could be done to strengthen surveillance among hospitalized SARI case-patients. Surveillance systems captured young children but lacked data on adults and the elderly. More data on risk groups for severe influenza in West Africa are needed to help shape influenza prevention and clinical management policies and guidelines.


    KEYWORDS:

    Epidemiology; Influenza; West Africa

    PMID: 29202715 DOI: 10.1186/s12879-017-2839-1
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