[Source: EuroFlu, full page: (LINK). Edited.]
EuroFlu - Weekly Electronic Bulletin - Week 52 : 23/12/2013-29/12/2013 - 03 January 2014, Issue No. 511
Influenza activity remains at low levels in the WHO European Region
Summary, week 52/2013
- The reporting of influenza surveillance data for week 52/2013 is incomplete due to the Christmas/New Year holidays and should be interpreted with caution.
- Consultation rates for influenza-like illness (ILI) and acute respiratory infections (ARI) in outpatient clinics were at low levels throughout the WHO European Region.
- However, the numbers of influenza A(H3N2), A(H1N1)pdm09 and influenza B detections have been increasing, with the majority being influenza A(H3).
- The number of reported hospitalizations due to severe acute respiratory infection (SARI) remained low, but 4 cases associated with influenza A infection were reported for week 52.
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 52/2013 the number of influenza detections in the Region increased compared with previous weeks, but the reported number of specimens tested was much lower.
In total, 3646 specimens from sentinel and non-sentinel sources were tested for influenza during week 52, 191 (5.2%) of which were positive: 177 (93%) influenza A and 14 (7%) influenza B (Figs. 1 and 2).
The results are affected by underreporting by several countries due to the Christmas/New Year holidays.
Of the 148 influenza A viruses that were subtyped during week 52/2013, 28 (19%) were A(H1N1)pdm09 and 120 (81%) A(H3N2) (Fig. 2a).
Since the beginning of weekly monitoring (week 40/2013), sentinel and non-sentinel sources have yielded 1399 influenza detections: 1172 (84%) were influenza A viruses and 227 (16%) influenza B (Fig. 2b).
Of the 819 influenza A viruses that have been subtyped, 303 (37%) were A(H1N1)pdm09 and 516 (63%) were A(H3N2) (Fig. 2b).
As the number of influenza detections remained low in week 52/2013, only 5 countries reported a dominant virus, influenza A (Norway, Switzerland), influenza A(H3) (Turkey), influenza A ((H1N1)pdm09 and H3) (Russian Federation) and influenza A(H1N1)pdm09 (Greece) 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, 5 countries (Denmark, Germany, Portugal, the Russian Federation and the United Kingdom (England)) have characterized 17 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
- 2 B/Victoria/2/87 lineage viruses (B/Brisbane/60/2008-like).
Nine countries (Denmark, Finland, Germany, the Netherlands, Norway, Portugal, Spain, Sweden and the United Kingdom (Scotland)) have characterized 69 influenza viruses genetically: 30 A(H3N2), 29 A(H1N1)pdm09, and 10 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 clade;
- the 29 A(H1N1)pdm09 viruses belonged to genetic group 6, represented by A/St Petersburg/27/2011;
- 1 influenza virus belonged to clade 1A of the B/Victoria lineage, represented by B/Brisbane/60/2008;
- of 9 B/Yamagata lineage viruses 6 belonged to clade 2, represented by B/Massachusetts/02/2012 and 3 to clade 3, represented by B/Wisconsin/1/2010.
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 52/2013 all European countries continued to report low influenza activity (Map 2) and mainly stable trends (Map 4), with predominantly no or sporadic influenza activity (Map 3).
During week 52/2013, consultation rates for ILI and/or ARI remained below the national baselines or at pre-season levels in all countries reporting clinical data, but this might be due to decreased reporting during the Christmas/New Year holiday period.
The number of ILI and ARI cases testing positive for influenza in the Region has been slowly increasing since week 48/2013. During week 52/2013, 89 sentinel samples tested positive for influenza; these were reported mainly by western European countries, but the number of specimens tested was less than in previous weeks due to the Christmas/New Year holidays.
During week 52/2013, 89 (23%) of the 387 specimens collected from sentinel sources tested positive for influenza, the majority being influenza A(H3) (Fig. 6a). 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, it remains at low levels in reporting countries participating in hospital surveillance for SARI in the WHO European Region (Fig. 7).
During week 52/2013, 4 of the 60 SARI samples collected in Belarus, Kazakhstan, the Republic of Moldova, Romania, the Russian Federation, and Ukraine tested positive for influenza A (2 – H3N2 and 2 – A(H1N1)pdm09) (Fig. 8a), which is in line with the results of outpatient surveillance. Click here for a detailed overview in table format.
Since week 40/2013, Ireland, France, Spain, Sweden and the United Kingdom have reported 59 hospitalized laboratory-confirmed influenza cases in total: 12 influenza B, 16 A(H1N1)pdm09, 4 A(H3) and 27 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 giving a slightly later start compared to 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.
For more information about the EUROMOMO mortality monitoring system please click here.
Country comments (where available)
- Republic of Moldova: 18 samples were tested for Influenza A and B - none of them were positive. 2 samples were positive for RNA hRSV, and 2- positive for RNA hParainfluenza virus type 3.
- Scotland: Please note that the GP consultation rates for ILI and ARI were adjusted to account for the reduced number of working days in week 52. The data for this week must be interpreted with caution.