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Influenza virus activity in the world, 5 August 2013 (WHO, edited): 55% isolates wk28_29 were H1pdm09, 45% H3N2

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  • Influenza virus activity in the world, 5 August 2013 (WHO, edited): 55% isolates wk28_29 were H1pdm09, 45% H3N2

    [Source: World Health Organization, full page: (LINK).]

    Influenza virus activity in the world, 5 August 2013

    Source: Laboratory confirmed data from the Global Influenza Surveillance and Response System (GISRS).

    Based on FluNet reporting (as of 30 July 2013, 12:30 UTC), during weeks 28 to 29 (7 July 2013 to 20 July 2013), National Influenza Centres (NICs) and other national influenza laboratories from 73 countries, areas or territories reported data.

    The WHO GISRS laboratories tested more than 24 825 specimens.

    1884 were positive for influenza viruses, of which 1590 (84.4%) were typed as influenza A and 294 (15.6%) as influenza B.

    Of the sub-typed influenza A viruses, 719 (54.9%) were influenza A(H1N1)pdm09, 590 (45%) were influenza A(H3N2) and 1 (0.1%) was influenza A(H3N2)v.

    Of the characterized B viruses, 8 (100%) belong to the B-Yamagata lineage and 0 (0%) to the B-Victoria lineage.


    During weeks 28 and 29, influenza increased in the southern hemisphere while it remained low in the northern hemisphere. A(H1N1)pdm09 viruses were the predominantly detected subtype globally, followed by A(H3N2) and influenza B viruses.

    In Oceania, increased A(H3N2) detections were reported from Australia with sporadic co-circulation of influenza A(H1N1)pdm09 and influenza B. In New Zealand influenza B activity increased.

    In Africa, influenza B viruses circulated throughout the region, however South Africa continued to report a predominance of A(H1N1)pdm09 viruses.

    Increased influenza activity due to A(H1N1)pdm09 and A(H3N2) was reported from a number of countries in the Central and South American region.

    In the temperate regions of South America, A(H1N1)pdm09 continued to co-circulate widely with influenza B viruses. Peru reported an increase in the detections of A(H1N1)pdm09 viruses.

    A(H1N1)pdm09 and A(H3N2) viruses circulated throughout Asia with increased A(H3N2) activity in parts of south east Asia such as Cambodia, India and Thailand. China reported co-circulation of A(H1N1)pdm09 and A(H3N2) viruses.

    Influenza activity remained low in the European region.

    In North America, seasonal influenza activity remained low in the United States of America. A total of 14 A(H3N2)v viruses have been reported in 2013.

    Click here for information from the Centers for Disease Control and Prevention (CDC), United States of America, about A(H3N2)v infections

    Click here for avian influenza A(H7N9) situation updates, risk assessment and other technical information