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Influenza Update N? 194, 16 September 2013 (WHO, edited)

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  • Influenza Update N? 194, 16 September 2013 (WHO, edited)

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

    Influenza Update N? 194, 16 September 2013

    • Influenza activity in the northern hemisphere temperate zones remained at inter-seasonal levels. The United States of America reported 18 cases of human infection with influenza A(H3N2)v this year, with the first case reported in June. More details can be found at
    • In most regions of tropical Asia influenza activity decreased.
    • In the Caribbean region of Centreal America and tropical South America the influenza season appeared to have come to an end. Respiratory Syncytial Virus, influenza A(H1N1)pdm09 and influenza A(H3N2) were the main respiratory viruses reported since May of this year.
    • Influenza activity peaked in the temperate countries of South America and in South Africa in late June. Influenza activity in these areas was primarily associated with influenza A(H1N1)pdm09 throughout the season, but since July greater numbers of influenza A(H3N2) and influenza type B viruses were observed.
    • In Australia and New Zealand, numbers of influenza viruses detected and rates of influenza-like illness were lower than those at same time in previous years, but showed an increasing trend since early August. Influenza A(H3N2) and type B were much more commonly detected than A(H1N1)pdm09 in both countries.
    • As of 16 September, a total of 135 cases of influenza A(H7N9) virus infection were reported. For more details see:

    Countries in the temperate zone of the northern hemisphere

    North America

    Overall influenza activity in North America remained at low levels throughout the region. In Canada and the United States of America, influenza activity remained at inter-seasonal levels.

    The USA has reported 18 human infections with influenza A(H3N2)v virus in 2013 since the first case in June. For more details see

    In Mexico influenza activity was low after a period of several weeks with higher influenza activity.


    Influenza activity in Europe remained at inter-seasonal levels. Consultation rates for influenza-like illness (ILI) and acute respiratory infection (ARI) were at low levels for all countries in the region. None of the specimens collected from sentinel sites tested positive for influenza.

    Northern Africa and the Western Asia region

    Influenza activity was low in the Northern Africa and western Asia regions.

    Northern Asia

    Influenza activity in the temperate region of Asia remained at inter-seasonal levels since late May.

    As of 11 August 2013, 135 cases of influenza A(H7N9) were identified, of which 44 died. There were no new cases since the last update. More and updated information is posted at:


    Countries in the tropical zone

    Tropical countries of the Americas/Central America and the Caribbean

    Overall influenza activity in the Caribbbean and Central America was at a low level throughout the region. A clear influenza season was seen in Costa Rica, Dominican Republic, El Salvador, Nicaragua and Panama, but influenza transmission had come to an end in the last few weeks in these countries. Co-circulation of influenza A(H1N1)pmd09 and influenza A(H3N2) continued in Cuba, but at low levels.


    In tropical South America, influenza activity decreased overall, indicating the end of the influenza season in this region.

    In Colombia, the proportions of outpatient visits, hospitalizations, and ARI-associated intensive care unit admissions did not change significantly from the previous week and showed an overall decreasing trend.

    In Venezuela, after having peaked in the beginning of June, the ARI and pneumonia levels returned to their expected activity levels for the time of the year. The percentage positive samples for respiratory virus decreased in the last weeks to zero.

    A decrease in SARI hospitalizations was also seen in Ecuador.

    A sharp increase in influenza A(H1N1)pdm09 transmission was however observed in Peru in the middle of July, but since the last few weeks transmission levels were decreasing in this country as well.

    In Plurinational State of Bolivia co-circulation of influenza A(H1N1)pdm09 and influenza B subtypes continued, but influenza transmission decreased over the last few weeks.

    Brazil showed a similar picture as the other countries in this region; the influenza virus detections in both ILI and SARI cases decreased.


    Central African tropical region

    Cote d?Ivoire, Ghana and Kenya reported circulating influenza virus.

    Cote d?Ivoire reported predominantly A(H1N1)pdm09 and influenza B transmission, whereas in Ghana, there were more detections of influenza A(H3N2).

    Kenya reported co-circulation of influenza A(H3N2) and B virus.

    Cameroon reported low influenza activity.

    After having peaked at the end of May, influenza activity in Madagascar continued to decrease and currently only influenza B has been detected.

    Tropical Asia

    Influenza transmission in southern Asia remained consistently low in all countries. Both influenza influenza A(H1N1)pdm09 and A(H3N2) viruses were reported in this area.

    In southern China and Hong Kong Special Administrative Region, a change in circulating influenza subtype from A(H1N1)pdm09 to A(H3N2) was observed over the last weeks.

    In Southeast Asia, influenza activity decreased with continued circulation of influenza A(H3N2) virus predominating in Thailand.


    Countries in the temperate zone of the southern hemisphere

    Temperate countries of South America

    As in the tropical countries of South America, in the temperate countries of South America the influenza season had come to an end as well.

    Influenza and RSV activity showed a decreasing trend and RSV continued to be the most commonly respiratory virus detected in temperate South America.

    In Chile, the national ILI consultation rate and the proportion of SARI-associated hospitalizations continued to decline. RSV remained the most common respiratory virus detected.

    In Argentina, the number of ILI and SARI cases peaked in late June, but declined since then. This decline was also reflected in the samples positive for influenza viruses.

    In Paraguay, influenza transmission has been decreasing since the beginning of July and in the last weeks hardly any influenza viruses were detected. To the contrast, ILI activity remained high.

    In Uruguay influenza activity continued to decrease. Influenza A(H1N1)pdm09 and RSV were the predominant respiratory viruses detected.


    Temperate countries of Southern Africa

    After a peak in influenza activity in South Africa due to influenza A(H1N1)pmd09 in June, a small second peak was observed in the last few weeks due to increased influenza A(H3N2) and influenza B circulation. This change of influenza subtype was seen in both ILI cases and SARI cases.


    Oceania, Melanesia and Polynesia

    ILI activity in Australia, New Zealand and the Pacific Islands showed an increasing trend during the last few weeks and may be indicating the start of a late season.

    Across jurisdictions of Australia the distribution of influenza types and subtypes was variable. In Western Australia, influenza A(H3N2) remained the predominant subtype, however the proportion of A(H1N1)pdm09 was increasing. Influenza type B continued to represent over half of Victoria's influenza notifications. In recent weeks there were increasing proportions of influenza B in South Australia, Queensland and New South Wales.

    Influenza positivity levels ranged from 19.0% in the national sentinel laboratory surveillance to 25.1% in the Australian Sentinel Practices Research Network (ASPREN) . Over the past few weeks the rate of seasonal increase in influenza associated hospitalisations stabilised. Almost 15% of influenza cases were admitted directly to ICU. The age distribution of hospital admissions showed peaks in the 0-9 and over 60 years age groups.

    In New Zealand, influenza activity continued to remain below the baseline threshold, but with increasing trends. 206 out of 383 samples received were positive for influenza: 68 were influenza B, 70 were influenza A(H3N2), 13 were influenza A(H1N1)pdm09 and 55 influenza A (not subtyped). In Auckland and Counties Manukau District Health Boards, influenza activity decreased slightly in community surveillance and hospital surveillance.


    Source of data

    The Global Influenza Programme monitors influenza activity worldwide and publishes an update every two weeks.

    The updates are based on available epidemiological and virological data sources, including FluNet (reported by the Global Influenza Surveillance and Response System) and influenza reports from WHO Regional Offices and Member States. Completeness can vary among updates due to availability and quality of data available at the time when the update is developed.

    Link to web pagesContact: