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Influenza virus activity in the world - 26 April 2013 (WHO, edited)

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  • Influenza virus activity in the world - 26 April 2013 (WHO, edited)

    [Source: World Health Organization, full page: (LINK). Edited.]
    Influenza virus activity in the world - 26 April 2013

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

    Based on FluNet reporting (as of 23 April 2013, 09:30 UTC), during weeks 14 to 15 (31 March 2013 to 13 April 2013), National Influenza Centres (NICs) and other national influenza laboratories from 78 countries, areas or territories reported data.

    The WHO GISRS laboratories tested more than 33 329 specimens. 6 194 were positive for influenza viruses, of which 2 856 (46.1%) were typed as influenza A and 3 338 (53.9%) as influenza B.

    Of the sub-typed influenza A viruses, 829 (45.8%) were influenza A(H1N1)pdm09 and 982 (54.2%) were influenza A(H3N2).

    Of the characterized B viruses, 218 (91.2%) belong to the B-Yamagata lineage and 21 (8.8%) to the B-Victoria lineage.


    During weeks 14 and 15 influenza activity was low in both the northern and southern hemispheres. Globally, a greater number of influenza B viruses were detected than influenza A.

    In the European region influenza B remained the predominant virus in the region but at a lower proportion compared to previous weeks.

    Influenza B viruses continued to circulate in the North American region, however, overall influenza activity remained low.

    Although influenza activity remained low in the Asian region, sporadic detections of influenza viruses were reported, the majority of which were A(H3N2) viruses.

    Sporadic influenza activity was reported from the African region in general with the exception of Madagascar which reported increased influenza B activity. A(H3N2) viruses continued to be detected in low numbers from the eastern parts of the continent.

    Sporadic influenza activity was reported from other parts of the world including countries in Central and South America, eastern Mediterranean and Oceania regions.

    China has continued to report new cases of avian influenza A(H7N9).

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

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