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

EuroFlu - Weekly Electronic Bulletin - Week 2 : 06/01/2014-12/01/2014 - 17 January 2014, Issue No. 513

Slow increase in influenza activity in Europe due to influenza A

Summary, week 2/2014
  • Despite an overall increasing trend in influenza detections, consultation rates for influenza-like illness (ILI) and acute respiratory infection (ARI) and hospitalization rates for severe acute respiratory infection (SARI) remained at low levels in most countries in the WHO European Region.
  • Influenza A(H3N2) accounted for most of the influenza detections in outpatient clinics and hospitals, in contrast to 2012/2013, when A(H1N1)pdm09 was the dominant virus.

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 02/2014 the number of influenza detections in the Region increased gradually from those in previous weeks.

In total, 7648 specimens from sentinel and non-sentinel sources were tested for influenza, 999 (13.1%) of which were positive: 953 (95%) influenza A and 46 (5%) influenza B (Fig. 1 and 2). Influenza A has remained dominant since week 40/2013.


Of the 641 influenza A viruses that were subtyped during week 02/2014, 291(45%) were A(H1N1)pdm09 and 350(55%) A(H3N2) (Fig. 2a).

This presents a very different picture from the same period in the 2012/2013 influenza season, when A(H1N1)pdm09 accounted for 84% of subtyped A viruses.

Since the beginning of weekly monitoring (week 40/2013), sentinel and non-sentinel sources have yielded 3888 influenza detections: 3546 (91%) were influenza A and 342 (9%) influenza B viruses (Fig. 2b).

Of the 2466 influenza A viruses that have been subtyped, 1199 (49%) were A(H1N1)pdm09 and 1267 (51%) were A(H3N2).



With an increase in the number of influenza detections, more countries reported data on dominant viruses during week 02/2014 than in previous weeks.

All countries (N=12) reported influenza A as the dominant type (Map 1 and Country table).

In countries providing data on dominant subtypes, influenza A(H3N2) was reported as dominant in Armenia and Turkey, while Bulgaria, Greece and Spain reported A(H1N1)pdm09 as dominant.

The Russian Federation 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.

Since week 40/2013, 6 countries (Denmark, Germany, Latvia, Portugal, the Russian Federation and the United Kingdom (England)) have characterized 34 influenza viruses antigenically:
  • 22 were A(H1N1)pdm09 viruses (A/California/7/2009 (H1N1)-like);
  • 9 were A(H3N2) viruses (A/Texas/50/2012 (H3N2)-like);
  • 2 B/Yamagata/16/88 lineage virus (1 B/Massachusetts/2/2012-like and 1 B/Wisconsin/1/2010-like) and
  • 1 B/Victoria/2/87 lineage viruses (B/Brisbane/60/2008-like).

10 countries (Belgium, Denmark, Finland, Germany, the Netherlands, Norway, Portugal, Spain, Sweden and the United Kingdom (Scotland)) have characterized 71 influenza viruses genetically: 28 A(H3N2), 31 A(H1N1)pdm09 and 12 influenza B viruses.
  • The 28 A(H3N2) viruses belonged to genetic subgroup 3C, represented by A/Texas/50/2012 in the A/Perth/16/2009 clade;
  • the 31 A(H1N1)pdm09 viruses belonged to genetic group 6, represented by A/St Petersburg/27/2011.

Of the 12 influenza B viruses, 1 belonged to clade 1A of the B/Victoria lineage, represented by B/Brisbane/60/2008; the 8 B/Yamagata lineage viruses belonged to clade 2, represented by B/Massachusetts/02/2012; and 3 belonged to clade 3, represented by B/Wisconsin/1/2010.

Since week 40/2013, 6 countries (the Netherlands, Norway, Portugal, Spain, Sweden and the United Kingdom (England)) have screened 72 influenza A(H1N1)pdm09, 36 influenza A(H3N2) and 7 influenza B viruses for susceptibility to oseltamivir and zanamivir.

All showed susceptibility to both drugs.

The 24 influenza A(H1N1)pdm09 and 18 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 02/2014, most European countries continued to report low-intensity influenza activity (Map 2), although with increasing trends (Map 4). As to geographic spread, influenza activity was predominantly sporadic (Map 3), with only Portugal, Spain and the United Kingdom (England) reporting widespread activity.

During week 02/2014, consultation rates for ILI and/or ARI continued to increase, but remained below the national thresholds or at low levels in all countries reporting clinical data, except Israel and the Netherlands.


The proportion of ILI and ARI cases testing positive for influenza in the Region has slowly increased since week 48/2013 (Fig. 5). During week 02/2014, 373 sentinel samples tested positive for influenza, with the majority reported by Spain and Turkey.


During week 2/2014, 373 (30%) of the 1261 specimens collected from sentinel sources tested positive for influenza, the majority being influenza A(H3N2), similarly to previous weeks (Fig. 6a). (Fig. 6a). Click here for a detailed overview in a table format.


Hospital surveillance for SARI

The number of SARI hospitalizations remains at low levels in reporting countries participating in hospital surveillance for SARI in the WHO European Region. A slight increase in influenza positivity rate was noted from week 50/2013 (Fig. 7).

In comparison with previous weeks, the SARI hospitalization rate appeared to decrease, but this might be due to decreased reporting during the holiday period.


During week 2/2014, 10 of the 98 (10%) SARI samples collected in Armenia, Belarus, Georgia, Kazakhstan, the Republic of Moldova, Romania, the Russian Federation, Serbia and Ukraine tested positive for influenza A with the majority being A(H3N2) (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, Romania, Spain, Sweden and the United Kingdom have reported 383 hospitalized laboratory-confirmed influenza cases in total: 14 influenza B, 191 A(H1N1)pdm09, 54 A(H3) and 124 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.

Pooled analysis of week data for 2/2014 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.


Country comments (where available)
  • Norway: Low-level co-circulation of influenza A(H1N1), A(H3N2) and B/Yamagata lineage viruses
  • Republic of Moldova: 1 sample was tested for Influenza A and B - none of them were positive.