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Influenza update - 18 November 2011 - Update number 147 (edited): H3 in Canada, A(H1N1)pdm09 in Nicaragua

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  • Influenza update - 18 November 2011 - Update number 147 (edited): H3 in Canada, A(H1N1)pdm09 in Nicaragua

    [Source: World Health Organization, full text: (LINK). Edited.]
    Influenza update - 18 November 2011 - Update number 147

    Please note that an expanded web version of the WHO Weekly Epidemiological Record on the review the 2011 influenza season of the southern hemisphere is available.

    • Influenza activity in the temperate regions of the northern hemisphere remains low or undetectable, though a recent outbreak of influenza A(H3N2) in a seniors lodge has been reported in Alberta, Canada.
    • Significant influenza activity was reported in only a few countries of the tropical zone including Nicaragua in the Americas, Cameroon in central Africa, and Cambodia in South East Asia.
    • Transmission in the temperate countries of the southern hemisphere has returned to intra-seasonal levels, with some persistence of influenza A(H3N2) in Australia.

    Countries in the temperate zone of the northern hemisphere

    The influenza season has not yet started in the northern hemisphere temperate zone, though some activity has been reported in a few areas.

    The majority of the countries in this zone reported low or no influenza activity in recent weeks.

    In Canada, one laboratory-confirmed influenza A(H3) outbreak was reported in a seniors lodge in Calgary, Alberta in week 44. It is the first outbreak due to influenza reported in Canada this season.

    In Europe, a number of countries including France, Norway, Sweden, Finland, the Czech Republic, and parts the western Russian Federation have reported sporadic influenza activity, however, there has not yet been an accompanying increase in influenza virus detections in these areas.

    Countries in the tropical zone

    Tropical countries of the Americas

    In the tropical countries of the Americas, generally low levels of influenza transmission were reported with the exception of Nicaragua where sharp increases in the numbers of influenza A(H1N1)pmd09 virus detections began in late September. Most cases reported in the country were in Managua, where 14 individuals with H1N1pdm infection were hospitalized. Much smaller numbers of influenza A(H3N2) have also been detected in the country.

    Transmission of H3N2 has decreased to low levels in El Salvador and Honduras after peaking in September.

    Sub-saharan Africa

    In sub-Saharan Africa, influenza transmission has generally remained low with the exception of Cameroon. In Cameroon, influenza type B transmission began in June and appears to be declining since peaking in early September and corresponded to a parallel rise in influenza-like illness (ILI) cases.

    Transmission of H1N1pdm, which began about six weeks after type B, appears to be peaking now coincident with a rise in H3N2 detections. Notably, more than 75% of the ILI cases reported through the sentinel surveillance system in Cameroon have been children under the age of 5 years.

    Tropical Asia

    Influenza transmission in tropical Asia is active in localized areas.

    Cambodia and Lao People's Democratic Republic report high level transmission of a mixture of H1N1pdm and influenza type B (Cambodia) and H1N1pdm (Lao People's Democratic Republic ) in the end of October. Sixty-five percent of ILI cases from sentinel sites in Cambodia tested positive, primarily of influenza type B (60%) and influenza A(H1N1)pdm09, with a small number of influenza A(H3N2).

    Viet Nam, in contrast, has continued to report sustained transmission of H1N1pdm for most of the year with a slight nadir occurring in June.

    Other countries of southern Asia reported small numbers of both H3N2 and influenza type B.

    Countries in the temperate zone of the southern hemisphere

    South America

    In the temperate regions of South America influenza transmission has declined to intra-seasonal levels and the season appears to be largely over. Low or no influenza transmission is reported in all countries.

    Southern Africa

    South Africa experienced a second peak of influenza transmission this season between late August and late October of influenza virus type B and A(H3N2), which followed an earlier peak of influenza A(H1N1)pdm09. This was manifested in the number of patients and virus detection rate of Severe Acute Respiratory Infections (SARI). Transmission of all influenza viruses has since declined to low levels.

    Australia, New Zealand and South Pacific

    Influenza activity is now at intra-seasonal levels in Australia and New Zealand, though low-level transmission of H3N2 appears to be ongoing in the former.

    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.