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Influenza Update N? 173 - 23 November 2012 (WHO, edited): H1pdm09 in Ghana & Ethiopia

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  • Influenza Update N? 173 - 23 November 2012 (WHO, edited): H1pdm09 in Ghana & Ethiopia

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


    Influenza Update N? 173 - 23 November 2012



    Summary
    • Countries of the Northern Hemisphere temperate region report increasing influenza virus detections, however none have crossed their seasonal threshold or announced the beginning of their season.
    • Countries in southern and south east Asia, except Cambodia, reported decreasing influenza virus detections. Cambodia has reported increased detections of influenza A(H3N2) for at least 6 weeks.
    • In Sub-Saharan Africa, Cameroon has continued to experience circulation of influenza A(H3N2) but appears to have peaked and the rate of detections has decreased. Ethiopia and Ghana reported increases in influenza A(H1N1)pdm09 while Madagascar, Kenya and Togo reported low circulation of mainly influenza B.
    • Influenza activity in the temperate countries of the Southern Hemisphere is now at inter-seasonal levels.


    Countries in the temperate zone of the Northern Hemisphere

    Countries of the temperate regions of the Northern Hemisphere reported continued increases in detection of influenza virus with an increase in rates of influenza-like illness (ILI) and per cent positivity of specimens tested. However, none have yet crossed their seasonal thresholds or announced the beginning of their seasons.



    North America

    Some of the southern states of the United States of America and Ontario in Canada have started to report an increase in influenza activity.

    In Canada, Ontario reported increased influenza activity but the other regions of the country reported none. Nationally, the proportion of outpatient visits that were due to ILI was 1.9% slightly lower than the previous week of 2.2% but continuing a general upward trend for at least the past 6 weeks.

    The percentage of clinical specimens testing positive for influenza virus increased from 2.8% to 5% in the previous reporting week. Eight influenza outbreaks have been reported, five in long term care facilities and three in other settings.

    Of the viruses detected, 92% (87/106) were influenza A and 8% were influenza B. Of the influenza A viruses with subtype information, of which 91% were A(H3N2) and 9% were A(H1N1)pdm09.

    In the United States of America, ILI consultation rates were at 1.4%, which is below the seasonal threshold (2.2%), and 7.5% of 4,147 specimens tested were positive for influenza.

    The geographic spread of influenza was reported as regional in four states; eight states reported local activity; the District of Columbia and 32 states reported sporadic activity.

    Among the positive influenza samples, 56% were influenza A and 44% influenza type B. Of the influenza A viruses with subtype information, 98% were influenza A(H3N2).

    Since October 2012, the Centre for Disease Control and Prevention in the United States of America has antigenically characterized 77 influenza viruses. All 41 A(H3N2) influenza viruses were A/Victoria/361/2011-like, the strain contained in the current trivalent seasonal vaccine.

    Of the 35 influenza B viruses characterized, 24 were B/Wisconsin/1/2010-like (B/Yamagata lineage) and 11 were from the B/Victoria lineage.

    (...)



    Europe

    Influenza detections throughout Europe remain low, and at inter-season levels.

    However, there are reports of sporadic activity from Austria, Belgium, the Czech Republic, Finland, France, Germany, Norway, and the United Kingdom.

    Consultation rates for ILI and acute respiratory infections (ARI) continued to be low throughout Europe but are starting to rise and become widespread, presumably due to other respiratory viruses rather than influenza given the low influenza positivity rates among sentinel samples from ILI.

    The proportion of samples from sentinel sites positive for influenza remained low but increasing, with 14 (2.3%) out of 608 samples testing positive, (10 influenza A, 5 of which were subtyped as (H3N2), and 4 influenza B (lineage undetermined)).

    From non-sentinel sites, 81 samples were positive (46 influenza A and 35 influenza B: 28 influenza A were subtyped as 7 A(H3N2) and 21 A(H1N1pdm09)).

    None of the SARI cases reported were positive for influenza.



    Northern Africa and the Eastern Mediterranean

    Some influenza activity has been noted in countries of the Middle East. Bahrain, Israel, Oman and Qatar have all reported increasing numbers of viruses in the past two to three weeks. Virus types and subtypes vary slightly between countries and numbers are small but influenza A(H1N1)pdm09 has generally been the most commonly detected virus in the area.



    Temperate Asia

    Northern China reported low influenza activity, with only 26 samples (2.8%) out of 922 positive for influenza. Of these, 96% were influenza A(H3N2).

    In Mongolia, ILI activity continued to increase, particularly in Selenghe province. Although the majority of ILI reported countrywide being attributed to non-influenza viruses, there was an increase in the number of samples testing positive for influenza, primarily A(H3N2).

    Japan has reported only 2 positive samples for influenza B (lineage undetermined).



    Countries in the tropical zone

    Tropical countries of the Americas

    Influenza B and influenza A(H3N2) activity has been noted in Costa Rica and Nicaragua but has peaked in recent weeks. RSV activity has also been noted in the area with Costa Rica, Honduras and Panama reporting cases.

    In the Caribbean, Jamaica has reported an increase of influenza B virus circulation and a high percent of positive samples for influenza virus.

    In Guadalupe and Martinique, the epidemic of respiratory syncytial virus continued to decrease.

    In the tropical zone of South America, influenza activity continued to decline with low numbers of virus detections being reported.

    In Brazil, the overall trend of influenza was decreasing with influenza A(H3N2) being the main virus detected.

    In Paraguay, low levels of influenza B and influenza A(H3N2) viruses are being reported.

    (...)



    Sub-Saharan Africa

    Cameroon was still experiencing circulation of mainly influenza A(H3N2), but appeared to have peaked and the rate of detections were decreasing.

    Ethiopia and Ghana reported increases in influenza A(H1N1)pdm09, while Madagascar, Kenya and Togo reported low circulation of mainly influenza B.

    (...)



    Tropical Asia

    Influenza transmission continued in parts of tropical Asia.

    India reported a continued decline in detections since peaking in mid-September. The most common influenza virus in the country was influenza A(H1N1)pdm09 with smaller amounts of type B.

    Detections in Sri Lanka, however, appeared to be increasing slightly with a higher proportion of A(H3N2) co-circulating with A(H1N1)pdm09 and influenza B.

    In Southern Asia, Lao PDR, Thailand and Viet Nam reported decreasing detections of influenza positive samples, while Cambodia reported an increase.

    The most commonly detected virus differed between the countries with Cambodia reporting A(H3N2) in the large majority of cases while Lao PDR and Thailand have had more A(H1N1). In contrast with the other countries in the region, Viet Nam has reported mostly influenza B in recent weeks with very few influenza A viruses detected.

    Influenza activity in Philippines, Singapore and southern China including SAR Hong Kong, remained at inter-seasonal levels.

    (...)



    Countries in the temperate zone of the southern hemisphere

    Influenza activity has continued to decline in all temperate countries of the southern hemisphere and is now at inter-seasonal level.

    The only notable activity was in the southern cone of South America where Chile has reported a minor, secondary wave of influenza B transmission after a predominant influenza A(H3N2) season which peaked around the beginning of July.

    (...)



    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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