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Influenza Update N° 195, 30 September 2013 (WHO, edited)

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  • Influenza Update N° 195, 30 September 2013 (WHO, edited)

    [Source: World Health Organization, full PDF document: (LINK). Extracts.]


    Influenza Update N° 195, 30 September 2013


    Summary
    • Influenza activity in the northern hemisphere temperate zones remained at inter-seasonal levels.
    • In most regions of tropical Asia influenza activity decreased, with the exception of Hong Kong Special Administrative Region, China, where influenza activity associated with A(H3N2) viruses increased.
    • In the Caribbean region of Central America and tropical South America the influenza season appeared to have come to an end. Acute respiratory infections continued to decline. Respiratory Syncytial Virus predominated, and 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.
    • Australia and New Zealand had a late start of a season in August. Influenza activity seemed to decrease in mid-September in Australia. Co-circulation of influenza A(H3N2), influenza A(H1N1)pdm09 and type B was reported in both countries.
    Additional and updated information on non-seasonal influenza viruses can be found at: http://who.int/influenza/human_animal_interface/HAI_Risk_Assessment/en/index.html

    (...)


    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. In Mexico influenza activity remained low after a period of two months (July – August) with higher influenza activity.


    Europe

    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.

    (...)


    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. Decreasing numbers of influenza A have been seen in Cuba, Dominican Republic, Panama and Nicaragua, and influenza transmission seems to have come to an end in the last few weeks in these countries. Co-circulation of influenza A(H1N1)pmd09 and influenza A(H3N2) was reported, and influenza B was reported in Honduras.

    (...)

    In tropical South America, influenza activity decreased overall, indicating the end of the influenza season in this region for 2013.

    In Colombia, the proportions of outpatient visits, hospitalizations, and acute respiratory infections (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.

    In Ecuador the proportion of SARI-related hospitalizations was stable in relation to previous weeks, but was higher than levels recorded for the same period last year.

    SARI hospitalization rates increased compared to previous weeks in Suriname, and ten SARI deaths were reported from February to August of 2013.

    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 influenza B transmission, while in Ghana, there were more detections of influenza A(H3N2). Kenya reported co-circulation of influenza A(H3N2), A(H1N1)pdm09 and B virus.

    Cameroon reported low influenza activity. After having peaked at the end of May, influenza activity in Madagascar has shown a slight increase from previous weeks and currently only influenza B has been detected.


    Tropical Asia

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

    Over the last month an increase in influenza transmission was seen in Hong Kong Special Administrative Region (SAR), China. The influenza transmission in Hong Kong SAR was predominated by influenza A(H3N2) virus. This increased transmission was also seen in the influenza associated hospital rates in this region; mainly rates among 0-4 year old and 65+ year old patients increased over the past month.

    Overall in Southeast Asia, influenza activity decreased. Also in Thailand, the influenza transmission showed a downward trend over the last few weeks, although, there was still some influenza A(H3N2) transmission reported. In the last week, the number of ILI patients also dropped below baseline level 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. Influenza and ARI activity were reported at expected levels for the time of year and respiratory syncytial virus (RSV) continued to be the most common respiratory virus detected in temperate South America.

    In Chile, the proportion of ILI-associated hospital emergencies was lower than values observed from the same period last year. RSV remained the most common respiratory virus detected.

    In Argentina, ILI and SARI activity has shown a decreasing trend.
    In Paraguay, influenza transmission has been decreasing since the beginning of July and in the last few weeks has consisted of mostly influenza B cases. In contrast, ILI activity remained high.

    In Uruguay SARI-associated hospitalizations decreased from levels reported early in September, but maintained an elevated level compared to the same time period last year.

    (...)


    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. The most recent reports contain only detections of influenza A(H3N2).This change of influenza subtype was seen in both ILI cases and SARI cases.

    (...)


    Oceania, Melanesia and Polynesia

    The influenza season in Australia, New Zealand and the Pacific Islands had in the beginning of August a very late start and was decreasing in mid September in most areas.

    In Australia, influenza activity increased over the month of August, and based on the notification from the National Notification of Disease Surveillance System, decreased since the middle of September. In the period from 17 August to 30 August 2013, the distribution of influenza types and subtypes was variable across jurisdictions of Australia. 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% (401/2114) in the national sentinel laboratory surveillance to 25.1% (49/195) in the Australian Sentinel Practices Research Network (ASPREN) . The Influenza Complications Alert Network (FluCAN) sentinel hospital surveillance system reported that in the last weeks of August the rate of seasonal increase in influenza associated hospitalisations stabilised. Almost 15% of influenza associated hospitalisations 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 was almost at the baseline threshold and still showed an increasing trend in mid-September. 194 out of 410 samples received in the last week were positive for influenza (47%): 69 were influenza B, 65 were influenza A(H3N2), 23 were influenza A(H1N1)pdm09 and 37 influenza A (not subtyped). Influenza activity was especially high in the Waitemata District Health Board with more than 400 ILI patients per 100 000 practice patients. In Auckland and Counties
    Manukau District Health Boards, influenza activity increased in community surveillance and hospital surveillance.

    (...)

    Additional and updated information on non-seasonal influenza viruses can be found at: http://who.int/influenza/human_animal_interface/HAI_Risk_Assessment/en/index.html


    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 fluupdate@who.int


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