20 Dec 2013

EuroFlu - Weekly Electronic Bulletin - Week 50 : 09/12/2013-15/12/2013 - 20 December 2013, Issue No. 509 (edited)

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

EuroFlu - Weekly Electronic Bulletin - Week 50 : 09/12/2013-15/12/2013 - 20 December 2013, Issue No. 509

Low influenza activity in Europe, but more countries reporting influenza detections

 

Summary, week 50/2013

  • Influenza activity remained low throughout the WHO European Region, with consultation rates for influenza-like illness (ILI) and acute respiratory infection (ARI) in outpatient clinics and admissions for severe acute respiratory infection (SARI) in hospitals at pre-season levels in the majority of countries.
  • The numbers of influenza A(H3N2), influenza B and influenza A(H1N1)pdm09 detections have been slowly increasing, mainly in western European countries, with the majority being influenza A.
  • Respiratory syncytial virus detections continued to increase in some countries, but detections remained lower than last season.

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 50/2013 the number of influenza detections in the Region increased slightly in comparison with previous weeks.

In total, 7241 specimens from sentinel and non-sentinel sources were tested for influenza during the week, 164 (2.3%) of which were positive: 150 (92%) for influenza A and 14 (8%) for influenza B (Fig. 1 and 2).

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Of the 78 influenza A viruses that were subtyped during week 50/2013, 41 (53%) were A(H1N1)pdm09 and 37 (47%) A(H3N2) (Fig. 2a).

Since the beginning of the season (week 40/2013), sentinel and non-sentinel sources have yielded 854 influenza detections: 665 (78%) were influenza A viruses and 189 (22%) influenza B (Fig. 2b).

Of the 434 influenza A viruses that have been subtyped, 210 (48%) were A(H1N1)pdm09 and 224 (52%) were A(H3N2).

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Since the number of influenza detections remained low in week 50/2013, only 3 countries reported a dominant virus, influenza A (Norway) and influenza A(H3N2) in Italy and Spain, as shown in Map 1.

 

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.

Since week 40/2013, 3 countries (Germany, Portugal and the United Kingdom (England)) have characterized 13 influenza viruses antigenically:

  • 9 were A(H1N1)pdm09 viruses (A/California/7/2009 (H1N1)-like);
  • 2 were A(H3N2) viruses (A/Texas/50/2012 (H3N2)-like); and
  • 2 B/Yamagata/16/88 lineage viruses (1 B/Massachusetts/2/2012-like and 1 B/Wisconsin/1/2010-like).

7 countries (Denmark, Finland, the Netherlands, Norway, Portugal, Spain and Sweden) have characterized 57 influenza viruses genetically: 25 A(H3N2), 26 A(H1N1)pdm09 and 6 influenza B-Yamagata lineage.

  • The 25 A(H3N2) viruses belonged to genetic subgroup 3C, represented by A/Texas/50/2012 in the A/Perth/16/2009, A(H3) clade;
  • the 26 A(H1N1)pdm09 viruses belonged to genetic group 6, represented by A/St Petersburg/27/2011; and
  • 4 influenza B viruses belonged to clade 2, represented by B/Massachusetts/02/2012 and 2 to clade 3, represented by B/Wisconsin/1/2010, all in the Yamagata lineage.

Since week 40/2013, 5 countries (the Netherlands, Norway, Spain, Sweden and the United Kingdom (England)) have screened 32 influenza A(H1N1)pdm09, 17 influenza A(H3N2) and 2 influenza B viruses for susceptibility to oseltamivir and zanamivir. All showed susceptibility to both drugs.

The 14 influenza A(H1N1)pdm09 and 12 influenza A(H3N2) viruses screened for susceptibility to adamantanes were found to be resistant.

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 (an egg-adapted virus antigenically like the cell-propagated prototype virus A/Victoria/361/2011) and B/Massachusetts/2/2012-like (Yamagata lineage) viruses in vaccines (see the WHO headquarters web site).

 

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

During week 50/2013 most European countries reporting qualitative indicators indicated low influenza activity (Map 2) and mainly stable trends (Map 4), with predominantly no or sporadic influenza activity (Map 3).

During week 50/2013, consultation rates for ILI and/or ARI remained below the national baselines or at pre-season levels in all countries reporting clinical data except, despite there being no influenza detections, for the Republic of Moldova.

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The number of ILI and ARI cases testing positive for influenza in the Region has been slowly increasing since the beginning of the season. However, during week 50/2013 only 48 sentinel samples tested positive for influenza, reported mainly by several western European countries.

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During week 50/2013, 48 (5.8%) of the 830 specimens collected from sentinel sources tested positive for influenza, with the majority being influenza A(H3). Click here for a detailed overview in a table format.

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Hospital surveillance for SARI

The number of SARI hospitalizations has been slowly increasing since week 40/2013. However, the number remained at inter-season levels in reporting countries participating in hospital surveillance for SARI in the WHO European Region (Fig. 7).

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Similarly to previous weeks, none of the 128 SARI samples collected in Belarus, Georgia, Kazakhstan, Kyrgyzstan, the Republic of Moldova, Romania, the Russian Federation, Serbia and Ukraine tested positive for influenza during week 50/2013. Click here for a detailed overview in table format.

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Since week 40/2013, Ireland, France, Spain, Sweden and the United Kingdom have reported 40 hospitalized laboratory-confirmed influenza cases in total, with 11 being influenza B, 11 A(H1N1)pdm09, 4 A(H3) and 14 type A not subtyped. 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 presented by countries reporting on RSV, the positivity rate has been gradually increasing since week 40/2013 with a slightly later start compared with 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 50/2013 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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Country comments (where available)

  • Czech Republic
    • Only non-flu viruses have been detected so far.
  • Republic of Moldova
    • 23 samples were tested for Influenza A and B - none of them were positive. 2 samples were positive for RNA hRSV, 2 samples - positive for RNA Rhinovirus, 1 - positive for RNA hRhinovirus and RNA hMetapneumovirus, 2- positive for RNA hParainfluenza virus type 1, and 2 samples - positive for RNA hCoronavirus (genotypes HKU-1, OC43).

 

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