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Influenza Update N? 207, 24 March 2014 (WHO, edited)

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  • Influenza Update N? 207, 24 March 2014 (WHO, edited)

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

    Influenza Update N? 207, 24 March 2014

    • Globally overall influenza activity continued declining, although an increase in influenza B activity was observed in parts of the world with less intensity compared to the earlier influenza A activity.
    • In North America, influenza activity continued its decreasing trend, with indicators suggesting the influenza season is coming to a close, despit that a small increase in detections of influenza B was noted in the region.
    • In Europe, influenza activity was variable among countries. In general acitivity increased in the eastern regions but decreased in the southwestern and northern regions. Influenza A(H1N1)pdm09 and A(H3N2) continued circulating with variable predominance among countries.
    • In Eastern Asia, overall activity declined with a slight increase of influenza B activity observed. In China, influenza activity remained stable after a decrease late Februrary. Influenza activity in Mongolia remained elevated.
    • In Tropical Asia, influenza activity largely continued to decline, except Thailand where sustained elevated activity of influenza A(H1N1)pdm09 and an increased proportion of influenza B were reported.
    • In Northern Africa and Western Asia, influenza activity decreased overall, however the proportion of influenza B positive samples has begun to increase.

    Based on FluNet reporting (as of 20 March 2014, 13:20 UTC), during weeks 9 to 10 (23 February 2014 to 8 March 2014), National Influenza Centres (NICs) and other national influenza laboratories from 96 countries, areas or territories reported data.

    The WHO GISRS laboratories tested more than 74 758 specimens.

    13 548 were positive for influenza viruses, of which 10 289 (75.9%) were typed as influenza A and 3259 (24.1%) as influenza B.

    Of the sub-typed influenza A viruses, 4470 (65%) were influenza A(H1N1)pdm09 and 2410 (35%) were influenza A(H3N2).

    Of the characterized B viruses, 222 (87.4%) belonged to the B-Yamagata lineage and 32 (12.6%) to the B-Victoria lineage.

    For updates on human infections with avian influenza A(H7N9) virus see the WHO website


    Countries in the temperate zone of the northern hemisphere

    North America

    In North America, overall influenza activity continued to decrease, with idicators showing the influenza season is coming to a close in the region. Proportionly a slight increase in influenza B virus detections has however been reported since early March of 2014.

    Canada experienced a continued decrease in overall influenza activity,with influenza A(H1N1)pdm09 remaining the predominant virus for this season. Recent increases ininfluenza B resulted in the overall percentage of positive influenza A and influenza B detections to be approximately equal during the week of March 2 - 8. The age group most affected by influenza this season has been adults aged 20-64, but increasing influenza B circulation is resulting in agreater impact on elderly and pediactric populations.

    In the United States of America (USA), influenza activity continued a downward trend from the previous weeks, with indicators suggesting the season is coming to a close. The proportion of deaths attributed to pneumonia and influenza was below the epidemic threshold. The proportion of outpatient visits for influenza-like illness (ILI) was 2.0%, which is at the national baseline. Influenza A(H1N1)pdm09 continued to be the predominant virus affecting the USA during this season.

    In Mexico, influenza activity continued to decrease, and pneumonia rates were within expected levels for this time of year. Acute Respiratory Infection (ARI) and the ILI/severe acute respiratory infections (SARI) associated medical visits also decreased from the previous week. Of the positive influenza samples, 90% were influenza A (70% A(H1N1)pdm09, 20% A(H3N2)) and 10% were influenza B.



    In the Europe, influenza activity varied by country or region, with differences seen in intensity, geographic spread, and trend. Countries with increasing trends include Austria, Azerbaijan, Croatia, Estonia, Netherlands, Kazakhstan, Malta, and Montenegro Romania, the UK (northern Ireland).

    Greece continued to report high intensity activity, with all other countries reporting medium or low intensity.

    Southern and western countries, such as Italy and Spain, appeared to have peaked earlier and are reporting decreasing trends the past four weeks, indicating a possible cessation of the influenza season in these areas.

    Overall, consultation rates for ILI and ARI decreased throughout most areas of Europe.

    Influenza A(H1N1)pdm09 and A(H3N2) viruses circulated throughout the region with variability in predominance or codominance among different countries in roughly equal proportions.

    In patients testing positive for influenza and needing hospitalization, Influenza A(H1N1)pdm09 was detected more often than A(H3N2). Sentinel surveillance had more A(H3N2) specimens, while total specimens had more A(H1N1)pdm09. Based on the various indicators for the influenza season, the predominant virus and severity of the season has varied considerably between countries.


    Northern Africa and the Western and Central Asia region

    In Central and Western Asia, influenza activity decreased to a large extent.

    Pakistan reported a decreasing number of positive influenza specimens and ILI cases. Influenza A activity continued to decrease in the Islamic Republic of Iran, while influenza B activity began to increase. Influenza activity remained low in the remainder of the region.

    Eastern Asia

    In the Eastern Asian region, overall influenza trends varied, however influenza activity is generally on the decline. Influenza A(H1N1)pdm09, A(H3N2), and influenza B viruses co-circulated, with influenza B increasing in proportion.

    In China, influenza activity and number of ILI reporting remained stable over the past two weeks in the north and south after decreasing in mid-February.

    Hong Kong Special Administrative Region of the People?s Republic of China reported continued high level of influenza activity despite a decrease since early March.

    ILI activity in Mongolia has decreased during the week of March 3 -9, however this proportion remains well above the country?s upper tolerance limit.

    Japan reports a decreasing number of ILI cases. Influenza activity continued to decrease in the Republic of Korea compared to a peak observed in February.

    Countries in the tropical zone

    Tropical countries of the Americas/Central America and the Caribbean

    Overall influenza activity in the Caribbean, Central America and tropical areas of South America was at low levels.

    Central African tropical region

    In Africa, influenza activity remained low.

    Mauritius reported increased influenza activity, all three subtypes were detected. Influenza B activity was reported from a number of countries but in low numbers.

    Tropical Asia

    Influenza activity among South-East Asian countries generally continued to decrease, with low levels in Cambodia, Lao PDR, and Viet Nam.

    Thailand reported a sustained increase in influenza activity and ILI cases with A(H1N1)pdm09 as the predominant virus, with an increasing proportion of influenza B.

    Countries in the temperate zone of the southern hemisphere

    In the Southern Hemisphere ILI activity remained relatively low, with low level circulation of influenza A(H1N1)pdm09, A(H3N2)and influenza B.


    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 WHO 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 pages