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EuroFlu - Weekly Electronic Bulletin - Week 15 : 07/04/2014-13/04/2014 - 18 April 2014, Issue No. 526: Sporadic flu activity in Europe

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  • EuroFlu - Weekly Electronic Bulletin - Week 15 : 07/04/2014-13/04/2014 - 18 April 2014, Issue No. 526: Sporadic flu activity in Europe

    [Source: EuroFlu, full page: (LINK). Edited.]


    EuroFlu - Weekly Electronic Bulletin - Week 15 : 07/04/2014-13/04/2014 - 18 April 2014, Issue No. 526

    Sporadic influenza activity in Europe


    Summary, week 15/2014
    • Influenza activity has returned to preseason level in most countries across the WHO European Region, while the percentages of influenza-like illness (ILI) and/or acute respiratory infection (ARI) sentinel specimens testing positive for influenza continued to decrease.
    • Influenza A(H1N1)pdm09 and A(H3N2) viruses continue to co-circulate in the Region, with very few influenza B detections having been reported throughout the season.
    • Countries with hospital surveillance for severe acute respiratory infection (SARI) continue to report SARI hospitalizations, but the numbers are declining overall, as are the proportion of samples testing positive for influenza.
    • The results of influenza activity for week 15/2014 should be interpreted with caution, since reporting by some countries was incomplete due to the holidays.

    The EuroFlu bulletin describes and comments on influenza activity in the 53 Member States in the WHO European Region to provide information to public health specialists, clinicians and the public on the timing of the influenza season, the spread of influenza, the prevalence and characteristics of circulating viruses (type, subtype and lineage) and severity.

    For a description of influenza surveillance in the WHO European Region see below.


    Virological surveillance for influenza

    During week 15/2014, both the total number of specimens tested for influenza and the positivity rate decreased, with a slight increase in the number of influenza B detections in comparison with previous weeks.

    7772 specimens from sentinel and non-sentinel sources were tested for influenza, 1084 (14%) of which were positive: 939 (87%) for influenza A and 145 (13%) for influenza B (Fig. 1 and 2).
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    Influenza A has remained the dominant virus type in circulation across the Region since the start of weekly monitoring in week 40/2013.

    Of the 541 influenza A viruses that were subtyped during week 15/2014, 217(40%) were A(H1N1)pdm09 and 324 (60%) A(H3N2) (Fig. 2a).

    Since week 40/2013, sentinel and non-sentinel sources have yielded 43385 influenza detections: 41118 (95%) were influenza A and 2267 (5%) influenza B viruses (Fig. 2b).

    Of the 28626 influenza A viruses that have been subtyped, 16417 (57%) were A(H1N1)pdm09 and 12209 (43%) were A(H3N2).

    In addition, the lineage of 176 influenza B viruses has been determined: 162 (92%) belonged to the B/Yamagata lineage (the lineage of the B virus recommended by WHO for inclusion in trivalent seasonal influenza vaccines) and 14 (8%) to the B/Victoria lineage.
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    With the decline of influenza activity in the Region, fewer countries than in previous weeks reported on dominant influenza type.

    Of the 29 countries supplying such data, only 12 reported influenza A as dominant in week 15/2014.

    Of countries providing data on dominant subtypes, influenza A(H3N2) was reported as dominant in 5 countries (Croatia, Germany, Ireland, Romania and the Russian Federation), while only Belarus and the United Kingdom (Wales) reported A(H1N1)pdm09 as dominant. France and Switzerland reported A(H1N1)pdm09 and A(H3N2) as co-dominant.


    Virus strain characterizations

    Circulating influenza viruses are assessed each season for their antigenic and genetic characteristics, to determine the extent of their antigenic similarity to the viruses included in the seasonal influenza vaccine, and determine the prevalence of mutations that affect pathogenicity or are associated with susceptibility to antiviral drugs.

    For the 2013/2014 northern hemisphere influenza season, WHO recommended inclusion of A/California/7/2009 (H1N1)pdm09-like, A/Texas/50/2012 (H3N2)-like and B/Massachusetts/2/2012-like (Yamagata lineage) viruses in vaccines (see the WHO headquarters web site).

    The WHO Consultation on the Composition of Influenza Virus Vaccines for the Northern Hemisphere 2014–2015 took place in week 7/2014, and the WHO expert group recommended no change from the vaccine composition for the 2013–2014 season. (see the WHO headquarters web site).

    Since week 40/2013, 1941 influenza viruses characterized antigenically by 15 countries (the Czech Republic, Denmark, Finland, Germany, Ireland, Latvia, the Netherlands, Norway, Portugal, Romania, the Russian Federation, Slovakia, Slovenia, Switzerland and the United Kingdom (England, Scotland)) corresponded with the viruses recommended by WHO for inclusion in the current northern hemisphere seasonal influenza vaccine (Fig. 3).

    14 countries (Belgium, the Czech Republic, Denmark, Finland, Germany, Greece, Ireland, the Netherlands, Norway, Portugal, the Russian Federation, Spain, Sweden and Switzerland) have characterized 949 influenza viruses genetically (Fig. 4).
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    # Included in the WHO-recommended composition of influenza virus vaccines for use in the 2013/2014 northern hemisphere influenza season.

    * Included in the WHO-recommended composition of influenza virus vaccines for use in the 2014 southern hemisphere influenza season.


    Monitoring of susceptibility to antiviral drugs

    Since week 40/2013, 12 countries (Germany, Greece, Italy, the Netherlands, Norway, Portugal, Romania, Spain, Sweden, Switzerland, the Russian Federation and the United Kingdom (England)) have screened 1469 viruses for susceptibility to the neuraminidase inhibitors oseltamivir and zanamivir.

    Of the 1019 A(H1N1)pdm09 viruses tested, 1003 showed susceptibility to both drugs; 16 viruses carrying the neuraminidase H275Y amino acid substitution, causing resistance to oseltamivir, were identified.

    Of these 16 viruses, 15 were detected in the United Kingdom in hospitalized patients, most of whom were treated with neuraminidase inhibitors, and 1 virus from Switzerland was detected in a hospitalized immunocompromised patient treated with oseltamivir.

    Of the 307 influenza A(H3N2) viruses tested, 306 showed susceptibility to both drugs.

    The remaining virus, detected in the United Kingdom in a hospitalized immunocompromised patient treated with oseltamivir, carried the neuraminidase E119V amino acid substitution, and showed reduced inhibition by oseltamivir but normal inhibition by zanamivir.

    All 43 influenza B viruses tested showed susceptibility to both oseltamivir and zanamivir.

    So far, there is no indication of increased resistance to the neuraminidase inhibitors during the season of 2013/2014. All 135 influenza A(H1N1)pdm09 and 96 influenza A(H3N2) viruses screened for susceptibility to adamantanes were found to be resistant.


    Outpatient surveillance for influenza-like illness (ILI) and/or acute respiratory infection (ARI)

    During week 15/2014, most European countries reported low-intensity influenza activity (Map 2), with only 3 countries reporting increasing trends (Map 4). As for geographic spread, influenza activity remained sporadic in most countries (Map 3).

    During week 15/2014, consultation rates continued to decline in most countries in the Region.

    Of the 22 countries with established national epidemic thresholds, the rates were had returned to or below the threshold level in almost all.

    In a number of northern, western and central countries (the Czech Republic, Denmark, Germany, Latvia, Lithuania, Luxembourg, the Netherlands, Norway, Slovakia, Switzerland and the United Kingdom (England)), consultation rates have remained very low since the beginning of the season (mostly below the threshold) and much lower than last season.

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    The percentage of positive sentinel ILI/ARI specimens continued to decrease. The percentage of positive specimens shows a very similar profile to that of the previous season, but at a significantly lower level throughout (Fig. 5).
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    During week 15/2014, 68 (14%) of the 489 specimens collected from sentinel sources tested positive for influenza virus; the majority were influenza A(H3N2) (Fig. 6a), similar to immediately preceding weeks. The number of influenza B detections remained low but has increased slightly over recent weeks. Click here for a detailed overview in a table format.
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    Hospital surveillance for SARI

    For sentinel surveillance of severe disease due to influenza, in week 15/2014 the number of SARI hospitalizations continued to decrease, with most cases reported being in those aged 0–4 years. The percentage of SARI patients who tested positive for influenza also decreased (Fig. 7).
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    During week 15/2014, 12(11%) of the 112 SARI samples collected through sentinel surveillance in Armenia, Belarus, Georgia, Kazakhstan, Kyrgyzstan, the Republic of Moldova, Romania, the Russian Federation, Serbia and Ukraine tested positive for influenza. the majority being influenza A(H3N2) in line with the results of sentinel ILI/ARI surveillance (Fig. 8a). Click here for a detailed overview in table format.
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    For week 15/2014, 4 countries (France, Ireland, Spain and Sweden) reported 40 hospitalized laboratory-confirmed influenza cases. Influenza A virus was detected in 39 cases and influenza B in 1.

    Since week 40/2013, 7 countries have reported 4582 hospitalized laboratory-confirmed influenza cases: 4527 (99%) were related to influenza virus type A infection and 55 (1%) to type B.

    Of 3100 subtyped influenza A viruses, 2299 (74%) were A(H1N1)pdm09 and 801 (26%) were A(H3N2).

    A higher proportion of A(H1N1)pdm09 viruses has been detected in patients in intensive care units (ICUs) (1326 out of 1550 subtyped: 86%) than in other hospitalized patients (973 out of 1550 subtyped: 63%).

    5 countries reported a total of 391 fatal case: 388 (99%) were associated with influenza virus type A infection and 3 (1%) with type B. Of 285 influenza A viruses subtyped from fatal cases, 230 (81%) were A(H1N1)pdm09 and 55 (19%) were A(H3N2).

    The results from SARI surveillance at sentinel hospitals reported to the WHO Regional Office for Europe (EuroFlu) and hospitalized laboratory-confirmed influenza cases reported to the European Centre for Disease Prevention and Control (ECDC) differ in that the former include a higher proportion of influenza A(H3N2) and a lower proportion of influenza A(H1N1)pdm09 than the latter. This pattern is most likely due to the circulation of the different influenza virus subtypes in countries.

    For more information on surveillance of confirmed hospitalized influenza, please see ECDC’s Weekly Influenza Surveillance Overview (WISO) at European Centre for Disease Prevention and Control web site.


    Respiratory syncytial virus (RSV)

    Based on the data reported by countries on RSV, detections peaked in week 50/2013 and have decreased in all the reporting countries since. This represents a slightly later start than in the previous season (see Country data and graphs for individual country data).


    EuroMOMO (European Mortality Monitoring Project)

    EuroMOMO is a project set up to develop and operate a routine public health mortality monitoring system to detect and measure, on a real-time basis, excess deaths related to influenza and other possible public health threats across 20 European Union (EU) countries.

    Pooled analysis of week data for 14/2014 showed that all-cause mortality was within the normal range for all reporting countries. Results of pooled analysis may vary, depending on which countries are included in the weekly analysis.

    For more information about the EUROMOMO mortality monitoring system please click here.

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