[Source: EuroFlu, full page: (LINK). Edited.]
EuroFlu - Weekly Electronic Bulletin, Week 51 : 16/12/2013-22/12/2013, 27 December 2013, Issue No. 510
Sporadic influenza detections in the WHO European Region
Summary, week 51/2013
- The reporting of influenza surveillance data for week 51/2013 is incomplete due to the Christmas holidays, which is also reflected in the lower number of tests performed.
- In most of the countries reporting data this week, consultation rates for influenza-like illness (ILI) and acute respiratory infections (ARI) remained at low levels, as would normally be seen outside the peak period for seasonal influenza.
- However, the numbers of influenza A(H3N2), influenza B and influenza A(H1N1)pdm09 detections have been slowly increasing, the majority being influenza A.
- The number of reported hospitalizations due to severe acute respiratory infection (SARI) has been also increasing slowly: 6 influenza A detections have been reported.
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 51/2013 the number of influenza detections in the Region increased slightly in comparison with previous weeks.
In total, 5942 specimens from sentinel and non-sentinel sources were tested for influenza during the week, 201 (3.4%) of which were positive: 183 (91%) for influenza A and 18 (9%) for influenza B (Figs. 1 and 2).
However, the results are affected by underreporting of western European countries due to the Christmas holidays.
Of the 106 influenza A viruses that were subtyped during week 51/2013, 24 (23%) were A(H1N1)pdm09 and 82 (77%) A(H3N2) (Fig. 2a).
Since the beginning of the season (week 40/2013), sentinel and non-sentinel sources have yielded 1129 influenza detections: 918 (81%) were influenza A viruses and 211 (19%) influenza B (Fig. 2b).
Of the 613 influenza A viruses that have been subtyped, 257 (42%) were A(H1N1)pdm09 and 356 (58%) were A(H3N2).
Since the number of influenza detections remained relatively low in week 51/2013, only 4 countries reported a dominant virus, influenza A (Norway and Switzerland) , influenza A(H3) (Turkey) and influenza A (pH1) (United Kingdom (Northern Ireland)) 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, 4 countries (Denmark, Germany, Portugal and the United Kingdom (England)) have characterized 16 influenza viruses antigenically:
- 9 were A(H1N1)pdm09 viruses (A/California/7/2009 (H1N1)-like);
- 4 were A(H3N2) viruses (A/Texas/50/2012 (H3N2)-like);
- 2 B/Yamagata/16/88 lineage viruses (1 B/Massachusetts/2/2012-like and 1 B/Wisconsin/1/2010-like) and
- 1 B/Victoria/2/87 lineage virus (B/Brisbane/60/2008-like).
Eight countries (Denmark, Finland, Germany, the Netherlands, Norway, Portugal, Spain, Sweden and the United Kingdom (Scotland)) have characterized 66 influenza viruses genetically: 25 A(H3N2), 26 A(H1N1)pdm09; and 6 influenza B viruses.
- The 30 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;
- 1 influenza virus belonged to clade 1A, represented by B/Brisbane/60/2008 in the Victoria lineage and
- 6 influenza B viruses belonged to clade 2, represented by B/Massachusetts/02/2012 and
- 3 to clade 3, represented by B/Wisconsin/1/2010, in the Yamagata lineage.
Since week 40/2013, 5 countries (the Netherlands, Norway, Spain, Sweden and the United Kingdom (England)) have screened 35 influenza A(H1N1)pdm09, 20 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 51/2013 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 51/2013, consultation rates for ILI and/or ARI remained below the national baselines or at pre-season levels in all countries reporting clinical data except for Albania and the Republic of Moldova.
The number of ILI and ARI cases testing positive for influenza in the Region has been slowly increasing since the beginning of the season. During week 51/2013, 66 sentinel samples tested positive for influenza; these were reported mainly by western European countries.
During week 51/2013, 66 (12%) of the 536 specimens collected from sentinel sources tested positive for influenza, the majority for influenza A(H3). Click here for a detailed overview in a table format.
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).
During week 51/2013, 6 of the 125 SARI samples collected in Armenia, Belarus, Georgia, Kazakhstan, the Republic of Moldova, Romania, the Russian Federation, Serbia and Ukraine tested positive for influenza A. Click here for a detailed overview in table format.
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 and picked up in week 50/2013 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 51/2013 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.
Country comments (where available)
Republic of Moldova: This week were detected 1 positive sample for Influenza A(H3N2) from 25 samples tested for Influenza viruses. Also, 1 sample was positive for RNA hRSV, 1 sample - positive for DNA Adenovirus, and 1 - positive for RNA hParainfluenza virus type 4.