EuroFlu - Weekly Electronic Bulletin - Week 6 : 03/02/2014-09/02/2014 - 14 February 2014, Issue No. 517
Influenza activity continues to increase across Europe
Summary, week 06/2014
- Consultation rates for influenza-like illness (ILI) and/or acute respiratory infection (ARI) are increasing in most countries in the WHO European Region.
- Overall, influenza activity across the Region appears less than that seen in the 2012?2013 season.
- Influenza activity is migrating from south to north, with some countries in the south probably having reached peak activity while those in the north show slow increases.
- While A(H1N1)pdm09 and A(H3N2) viruses are co-circulating, A(H1N1)pdm09 remains predominant in all parts of the Region but western Asia, where most influenza cases were due to A(H3N2).
- Influenza detections in the hospital sector show a similar situation, in which most severe acute respiratory infection (SARI) cases reported by countries in eastern Europe and western Asia were due to A(H3N2) and most hospitalized laboratory-confirmed influenza cases reported by western European countries were due to A(H1N1)pdm09.
- Overall, countries with SARI surveillance reported fewer influenza detections; this can be explained by low influenza activity in most of these countries up to week 06/2014.
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.
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Virological surveillance for influenza
During week 06/2014, a total of 12 748 specimens from sentinel and non-sentinel sources was tested for influenza, 2636 (21%) of which were positive: 2551 (97%) influenza A and 85 (3%) influenza B (Fig. 1 and 2).
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Influenza A has remained the dominant virus type across the Region since week 40/2013.
Of the 1538 influenza A viruses that were subtyped during week 06/2014, 1047 (68%) were A(H1N1)pdm09 and 491 (32%) A(H3N2) (Fig. 2a).
Since the beginning of weekly monitoring (week 40/2013), sentinel and non-sentinel sources have yielded 14 743 influenza detections, with an increasing proportion of influenza A viruses: 14 094 (96%) were influenza A and 649 (4%) influenza B viruses (Fig. 2b).
Of the 10 292 influenza A viruses that have been subtyped, 6360 (62%) were A(H1N1)pdm09 and 3932 (38%) were A(H3N2).
In addition, since week 40/2013, the lineage of 76 influenza B viruses has been determined: 70 (92%) belonged to the B/Yamagata lineage (the B lineage virus recommended by WHO for inclusion in trivalent seasonal influenza vaccines) and 6 (8%) to B/Victoria.
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For week 06/2014, 25 countries 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 6 countries (Georgia, Germany, Italy, Romania, Slovenia and Ukraine), while 13 countries (Bulgaria, Denmark, Estonia, Finland, Greece, Hungary, Iceland, Latvia, the Netherlands, Norway, Spain, Sweden and the United Kingdom (Scotland)) reported A(H1N1)pdm09 as dominant. 5 countries (France, Ireland, Luxembourg, 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.
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 and B/Massachusetts/2/2012-like (Yamagata lineage) viruses in vaccines (see the WHO headquarters web site).
Since week 40/2013, 341 influenza viruses characterized antigenically by 11 countries (Denmark, Finland, Germany, Latvia, Norway, Portugal, Romania, the Russian Federation, Slovakia, Switzerland and the United Kingdom (England)) corresponded with the viruses recommended by WHO for inclusion in the current northern hemisphere seasonal influenza vaccine (Fig. 3).
11 countries (Belgium, Denmark, Finland, Germany, Greece, the Netherlands, Norway, Portugal, the Russian Federation, Spain and Sweden) have characterized 361 influenza viruses genetically (Fig. 4).
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# Included in the WHO-recommended composition of influenza virus vaccines for use in the 2013/2014 northern hemisphere influenza season.
* Included in the WHO-recommended composition of influenza virus vaccines for use in the 2014 southern hemisphere influenza season.
Monitoring of susceptibility to antiviral drugs
Since week 40/2013, 8 countries (Greece, the Netherlands, Norway, Portugal, Spain, Sweden, the Russian Federation and the United Kingdom (England)) have screened 434 viruses for susceptibility to the neuraminidase inhibitors oseltamivir and zanamivir.
Of the 327 A(H1N1)pdm09 viruses tested, 325 showed susceptibility to both drugs.
2 viruses carrying the neuraminidase H275Y amino acid substitution, causing resistance to oseltamivir, were detected in the United Kingdom in hospitalized patients treated with oseltamivir.
Of the 84 influenza A(H3N2) viruses tested, 83 showed susceptibility to both drugs.
The remaining virus, detected in the United Kingdom in a hospitalized immunocompromised patient treated with oseltamivir, carried the neuraminidase E119V amino acid substitution and showed reduced inhibition by oseltamivir but normal inhibition by zanamivir.
All 23 influenza B viruses tested showed susceptibility to both oseltamivir and zanamivir.
So far, there is no indication of increased resistance to the neuraminidase inhibitors during the winter of 2013?2014.
All 62 influenza A(H1N1)pdm09 and 49 influenza A(H3N2) viruses screened for susceptibility to adamantanes were found to be resistant.
Outpatient surveillance for influenza-like illness (ILI) and/or acute respiratory infection (ARI)
During week 06/2014, most European countries continued to report low-intensity influenza activity (Map 2), with increasing trends (Map 4).
Regarding geographic spread, influenza activity was predominantly regional or widespread, particularly in countries in southern and western Europe (Map 3).
During week 06/2014, consultation rates increased in most countries in the Region. In most of the 22 countries with established national thresholds, the rates had reached or surpassed threshold levels.
At the same time, however, consultation rates continued to decrease in Bulgaria, Portugal, Spain and Turkey, where the influenza season started earlier.
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During week 06/2014, 557 sentinel specimens tested positive for influenza. The percentage of sentinel ILI/ARI specimens testing positive for influenza in week 06/2014 is much lower than that reported in week 06/2013 (Fig. 5). The proportions of influenza-positive respiratory specimens from ILI and ARI patients have most likely peaked in some countries, while increasing in others.
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During week 06/2014, 557 (30%) of the 1876 specimens collected from sentinel sources tested positive for influenza, the majority being influenza A(H1N1)pdm09 (Fig. 6a). Click here for a detailed overview in a table format.
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Hospital surveillance for SARI
Within the surveillance of severe disease due to influenza, the number of SARI hospitalizations and the percentage positive for influenza increased slightly from previous weeks, with most cases occurring in those aged 0?4 years (Fig. 7).
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During week 06/2014, 52 (29%) of the 182 SARI samples collected in Armenia, Belarus, Georgia, Kazakhstan, Kyrgyzstan, the Republic of Moldova, Romania, the Russian Federation, Serbia and Ukraine tested positive for influenza A, the majority being A(H3N2) (Fig. 8a). Click here for a detailed overview in table format.
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For week 06/2014, 5 countries (France, Ireland, Romania, Spain, and Sweden) reported 165 hospitalized laboratory-confirmed influenza cases, including 53 cases admitted to intensive care units (ICUs).
Since week 40/2013, 6 countries have reported 1941 hospitalized, laboratory-confirmed influenza cases: 1920 (99%) were related to influenza virus type A infection and 21 (1%) to type B.
Of 1322 subtyped influenza A viruses, 1054 (80%) were A(H1)pdm09 and 268 (20%) were A(H3N2).
5 countries reported a total of 158 fatal cases, all of which were associated with influenza A infection. Of these, 117 were subtyped: 94 (80%) as A(H1)pdm09 and 23 (20%) as A(H3).
SARI and hospitalized laboratory-confirmed influenza cases reported to the European Centre for Disease Prevention and Control (ECDC) differ in that the former include a higher proportion of influenza B and a lower proportion of influenza A(H1N1)pdm09 than the latter.
Overall, fewer influenza detections were reported in countries with SARI surveillance, which can be explained by low influenza activity in most of these countries up to week 06/2014. Further, the participating countries use different surveillance systems and this may lead to differences in influenza (sub)type detections.
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 had been gradually increasing since week 40/2013, peaked in week 50/2013 and has decreased in all the reporting countries since. This represents a slightly later start than in 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 06/2014 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.
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Country comments (where available)
Republic of Moldova: This week were tested for Influenza A and B 30 samples: 12 of them were positive for RNA Influenza virus A(H3N2) and 1 - for RNA h RSV.
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