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EuroFlu - Weekly Electronic Bulletin - Week 1 : 31/12/2012-06/01/2013 - 11 January 2013, Issue N? 470 (edited): 81% of positive samples were H1N1pdm09
[Source: EuroFlu, full page: (LINK). Edited.]
EuroFlu - Weekly Electronic Bulletin - Week 1 : 31/12/2012-06/01/2013 - 11 January 2013, Issue N? 470
Influenza activity gradually increasing in the WHO European Region
Summary, week 1/2013
For a description of influenza surveillance in the WHO European Region see below.
Virological surveillance for influenza
The proportion of specimens testing positive for influenza has increased steadily in the past weeks to 37%, mainly due to influenza viruses detected in the western part of the Region. This increase is attributable mainly to an increase of influenza A viruses.
Overall, a total of 2606 specimens tested positive for influenza in week 01/2013, the majority of which, 1829 (70%), were influenza A (Fig. 1).
The proportion of influenza A(H1N1)pdm09 relative to A(H3N2) is increasing.
Of the influenza A viruses, 779 were subtyped: 151(19%) as A(H3N2) and 628 (81%) as A(H1N1)pdm09 with mainly northern and central countries reporting A(H1N1)pdm09 detections (Fig. 2a).
Since week 40/2012, 7696 influenza viruses from sentinel and non-sentinel sources have been typed: 4914 (64%) were influenza A and 2782 (36%) influenza B (Fig. 2b).
Of the influenza A viruses 2502 were subtyped: 1051 (42%) as A(H3N2) and 1451(58%) as A(H1N1)pdm09 (Fig 2).
Overall, the proportion of influenza A(H1N1)pdm09 detections reported since week 40/2012 is considerably higher than in the same period last season, when A(H1N1)pdm09 represented less than 5% of total influenza A viruses subtyped.
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In week 01/2013, countries mainly in western and northern parts of the Region reported virus dominance: B in Belgium, Italy, Spain and the United Kingdom (Northern Ireland and Wales);A in Israel, the Netherlands and the United Kingdom (Scotland); co-dominance of type B and A(H1N1)pdm09 in France, Luxembourg and Switzerland; A(H1N1)pdm09 in the Czech Republic, Germany, Latvia, Lithuania, Norway and Poland; and A(H3N2) in Denmark, (Map 1). At this stage, it is therefore not clear which, if any, influenza type/subtype will dominate this season.
Virus strain characterizations
In the 2012/2013 northern hemisphere influenza season, WHO recommends inclusion of A/California/7/2009 (H1N1)pdm09-like, A/Victoria/361/2011 (H3N2)-like and B/Wisconsin/1/2010-like (from the B/Yamagata lineage) viruses in trivalent vaccines (see more at WHO web site).
Since week 40/2012, 85 influenza viruses characterized antigenically by 7 countries (Denmark, the United Kingdom (England), Germany, Latvia, Portugal, Romania, Switzerland) corresponded with the viruses recommended by WHO for inclusion in the current northern hemisphere seasonal influenza vaccine (Fig. 3). 8 countries (Belgium, Denmark, Finland, Germany, Norway, Portugal, Spain, Sweden) have characterized 118 influenza viruses genetically (Fig. 4).
# Included in the WHO-recommended composition of influenza virus vaccines for use in the 2012/2013 northern hemisphere influenza season.
* Included in the WHO-recommended composition of influenza virus vaccines for use in the 2013 southern hemisphere influenza season.
Monitoring of susceptibility to antiviral drugs
Since week 40/2012, 7 countries (Denmark, Germany, the Netherlands, Norway, Spain, Sweden and the United Kingdom) have screened 81 viruses for susceptibility to the neuraminidase inhibitors oseltamivir and zanamivir.
The 37 influenza A(H3N2) viruses, 28 A(H1N1)pdm09 viruses and 16 influenza B viruses showed susceptibility to both drugs.
The 14 influenza A(H3N2) and 5 influenza A(H1N1)pdm09 viruses screened for susceptibility to adamantanes were found to be resistant.
Outpatient surveillance for influenza-like illness (ILI) and/or acute respiratory infection (ARI)
Intensity remains low in most of the countries in the WHO European Region (Map 2) with most of the western countries reporting regional or widespread circulation of influenza for week 01/2013 (Map 3).
Consultation rates for ILI and ARI continue to increase (above the established baselines for Belgium, Denmark, Ireland and the Netherlands) throughout the northern and western parts of the Region and Israel, while remaining low in the eastern and southern parts of the Region (Map 4).
(?)
Concurrent with the increasing outpatient consultation rates, the influenza-positivity rate among ILI and ARI cases from sentinel sources is gradually increasing, mainly owing to detections in western Europe: overall, 345 (37%) of 943 specimens tested positive for influenza in week 01/2013 (Fig. 5).
Of the 345 positive specimens from sentinel sources, influenza A and influenza B were detected in similar proportions (Fig. 6a). Fig. 6b gives a detailed overview of cumulative influenza virus detections by type and subtype since week 40/2012. Click here for a detailed overview in a table format.
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Hospital surveillance for SARI
Hospitalizations due to SARI have remained stable overall, with most cases being reported in children aged 0?4 years (Fig. 7).
In the last few weeks, only sporadic influenza detections have been reported among SARI cases (Fig. 7), consistent with the overall low influenza activity in countries reporting on SARI hospitalizations.
In week 01/2013, 4 countries (Belgium, Kazakhstan, Kyrgyzstan and Ukraine) reported 9 cases positive for influenza virus among 110 specimens collected from hospitalized SARI cases in 6 countries (Belgium, Kazakhstan, Kyrgyzstan, Romania, the Russian Federation and Ukraine) (Fig. 8a).
Since week 40/2012, 1762 SARI specimens have been collected and tested for influenza. Click here for a detailed overview in table format.
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The countries notifying the European Centre for Disease Prevention and Control (ECDC) of severe influenza in hospitals, a higher number of influenza detections has been reported, reflecting increasing levels of influenza activity in the western part of the Region. To date, A(H1N1)pdm09, A(H3N2) and influenza B have been detected among hospitalized patients.
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.
N.B. 5 influenza-positive SARI cases reported by Belgium are not included in pie-chart this week
Description of influenza surveillance
Most of the 53 Member States of the WHO European Region monitor influenza activity through surveillance of ILI and/or ARI in primary care clinics, with some countries also conducting hospital-based surveillance for severe disease. Surveillance data in the Region are collected from sentinel and non-sentinel systems. Sentinel data come from a network of designated clinicians who routinely and systematically collect respiratory specimens from ILI, ARI or SARI cases according to standard case definitions. Non-sentinel data come from a variety of other sources, including community outbreaks, general practitioners and hospitals that are not part of the sentinel surveillance system for influenza and may not use a standard case definition for ILI, ARI or SARI. The EuroFlu bulletin collates and interprets epidemiological and virological data from the different surveillance systems in the Region, to provide information on the timing of the influenza season, the spread of influenza, the prevalence and characteristics of circulating influenza viruses according to influenza type and subtype (A(H3N2) and A(H1N1)pdm09) or lineage (B/Victoria of B/Yamagata), and severity. In addition, influenza viruses are assessed each season for their antigenic and genetic characteristics, to determine the extent of their antigenic and genetic similarity to the viruses included in the seasonal influenza vaccine and the prevalence of mutations that affect pathogenicity or are associated with reduced susceptibility to antiviral drugs.
(?)
Country comments (where available)
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EuroFlu - Weekly Electronic Bulletin - Week 1 : 31/12/2012-06/01/2013 - 11 January 2013, Issue N? 470
Influenza activity gradually increasing in the WHO European Region
Summary, week 1/2013
- Levels of influenza activity in countries in the WHO European Region are heterogeneous, with widespread activity mainly in the western and northern parts of the Region and no or sporadic activity in the eastern part, but a gradual increase overall.
- Influenza A(H1N1)pdm09, A(H3N2) and type B viruses continue to co-circulate, but the proportion of A(H1N1)pdm09 relative to A(H3N2) is increasing.
- The number of reported hospitalizations due to severe acute respiratory infection (SARI) remains stable, with 8% of cases being associated with influenza detection.
For a description of influenza surveillance in the WHO European Region see below.
Virological surveillance for influenza
The proportion of specimens testing positive for influenza has increased steadily in the past weeks to 37%, mainly due to influenza viruses detected in the western part of the Region. This increase is attributable mainly to an increase of influenza A viruses.
Overall, a total of 2606 specimens tested positive for influenza in week 01/2013, the majority of which, 1829 (70%), were influenza A (Fig. 1).
Of the influenza A viruses, 779 were subtyped: 151(19%) as A(H3N2) and 628 (81%) as A(H1N1)pdm09 with mainly northern and central countries reporting A(H1N1)pdm09 detections (Fig. 2a).
Since week 40/2012, 7696 influenza viruses from sentinel and non-sentinel sources have been typed: 4914 (64%) were influenza A and 2782 (36%) influenza B (Fig. 2b).
Of the influenza A viruses 2502 were subtyped: 1051 (42%) as A(H3N2) and 1451(58%) as A(H1N1)pdm09 (Fig 2).
Overall, the proportion of influenza A(H1N1)pdm09 detections reported since week 40/2012 is considerably higher than in the same period last season, when A(H1N1)pdm09 represented less than 5% of total influenza A viruses subtyped.
(?)
In week 01/2013, countries mainly in western and northern parts of the Region reported virus dominance: B in Belgium, Italy, Spain and the United Kingdom (Northern Ireland and Wales);A in Israel, the Netherlands and the United Kingdom (Scotland); co-dominance of type B and A(H1N1)pdm09 in France, Luxembourg and Switzerland; A(H1N1)pdm09 in the Czech Republic, Germany, Latvia, Lithuania, Norway and Poland; and A(H3N2) in Denmark, (Map 1). At this stage, it is therefore not clear which, if any, influenza type/subtype will dominate this season.
Virus strain characterizations
In the 2012/2013 northern hemisphere influenza season, WHO recommends inclusion of A/California/7/2009 (H1N1)pdm09-like, A/Victoria/361/2011 (H3N2)-like and B/Wisconsin/1/2010-like (from the B/Yamagata lineage) viruses in trivalent vaccines (see more at WHO web site).
Since week 40/2012, 85 influenza viruses characterized antigenically by 7 countries (Denmark, the United Kingdom (England), Germany, Latvia, Portugal, Romania, Switzerland) corresponded with the viruses recommended by WHO for inclusion in the current northern hemisphere seasonal influenza vaccine (Fig. 3). 8 countries (Belgium, Denmark, Finland, Germany, Norway, Portugal, Spain, Sweden) have characterized 118 influenza viruses genetically (Fig. 4).
* Included in the WHO-recommended composition of influenza virus vaccines for use in the 2013 southern hemisphere influenza season.
Monitoring of susceptibility to antiviral drugs
Since week 40/2012, 7 countries (Denmark, Germany, the Netherlands, Norway, Spain, Sweden and the United Kingdom) have screened 81 viruses for susceptibility to the neuraminidase inhibitors oseltamivir and zanamivir.
The 37 influenza A(H3N2) viruses, 28 A(H1N1)pdm09 viruses and 16 influenza B viruses showed susceptibility to both drugs.
The 14 influenza A(H3N2) and 5 influenza A(H1N1)pdm09 viruses screened for susceptibility to adamantanes were found to be resistant.
Outpatient surveillance for influenza-like illness (ILI) and/or acute respiratory infection (ARI)
Intensity remains low in most of the countries in the WHO European Region (Map 2) with most of the western countries reporting regional or widespread circulation of influenza for week 01/2013 (Map 3).
Consultation rates for ILI and ARI continue to increase (above the established baselines for Belgium, Denmark, Ireland and the Netherlands) throughout the northern and western parts of the Region and Israel, while remaining low in the eastern and southern parts of the Region (Map 4).
(?)
Concurrent with the increasing outpatient consultation rates, the influenza-positivity rate among ILI and ARI cases from sentinel sources is gradually increasing, mainly owing to detections in western Europe: overall, 345 (37%) of 943 specimens tested positive for influenza in week 01/2013 (Fig. 5).
(?)
Hospital surveillance for SARI
Hospitalizations due to SARI have remained stable overall, with most cases being reported in children aged 0?4 years (Fig. 7).
In week 01/2013, 4 countries (Belgium, Kazakhstan, Kyrgyzstan and Ukraine) reported 9 cases positive for influenza virus among 110 specimens collected from hospitalized SARI cases in 6 countries (Belgium, Kazakhstan, Kyrgyzstan, Romania, the Russian Federation and Ukraine) (Fig. 8a).
Since week 40/2012, 1762 SARI specimens have been collected and tested for influenza. Click here for a detailed overview in table format.
(?)
The countries notifying the European Centre for Disease Prevention and Control (ECDC) of severe influenza in hospitals, a higher number of influenza detections has been reported, reflecting increasing levels of influenza activity in the western part of the Region. To date, A(H1N1)pdm09, A(H3N2) and influenza B have been detected among hospitalized patients.
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.
N.B. 5 influenza-positive SARI cases reported by Belgium are not included in pie-chart this week
Description of influenza surveillance
Most of the 53 Member States of the WHO European Region monitor influenza activity through surveillance of ILI and/or ARI in primary care clinics, with some countries also conducting hospital-based surveillance for severe disease. Surveillance data in the Region are collected from sentinel and non-sentinel systems. Sentinel data come from a network of designated clinicians who routinely and systematically collect respiratory specimens from ILI, ARI or SARI cases according to standard case definitions. Non-sentinel data come from a variety of other sources, including community outbreaks, general practitioners and hospitals that are not part of the sentinel surveillance system for influenza and may not use a standard case definition for ILI, ARI or SARI. The EuroFlu bulletin collates and interprets epidemiological and virological data from the different surveillance systems in the Region, to provide information on the timing of the influenza season, the spread of influenza, the prevalence and characteristics of circulating influenza viruses according to influenza type and subtype (A(H3N2) and A(H1N1)pdm09) or lineage (B/Victoria of B/Yamagata), and severity. In addition, influenza viruses are assessed each season for their antigenic and genetic characteristics, to determine the extent of their antigenic and genetic similarity to the viruses included in the seasonal influenza vaccine and the prevalence of mutations that affect pathogenicity or are associated with reduced susceptibility to antiviral drugs.
(?)
Country comments (where available)
- Czech Republic: Up to end of week 1/2013 a cumulative total of 33 severe influenza patients with laboratory-confirmed influenza A(H1N1)2009 or influenza A(unsubtyped) were reported by intensive and resuscitation care units including 4 death.
- Norway: The number of influenza virus detections increased to a high level in week 1/2013. There appears to be local variation in the occurrence of A(H1N1)pdm09, A(H3N2), and B/Yamagata lineage viruses, but A(H1N1)pdm viruses are now predominating at the national level.
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