[Source: EuroFlu, full page: (LINK). Edited.]
EuroFlu - Weekly Electronic Bulletin - Week 51 : 17/12/2012-23/12/2012 - 28 December 2012, Issue N° 468
Influenza activity is increasing slowly in the WHO European Region
Summary, week 51/2012
- Influenza activity is slowly increasing with more countries in different parts of the Region reporting sporadic co-circulation of influenza A(H1N1)pdm09, A(H3N2) and type B viruses.
- This week the reporting of influenza surveillance data is incomplete due to the Christmas holidays. This is reflected in the lower number of testing performed. However the percentage of influenza-positive samples from both sentinel and non-sentinel sources are similar to last week.
- The number of reported hospitalizations due to severe acute respiratory infection (SARI) remains similar to that seen in the previous several weeks: 1 influenza detection was reported (influenza B).
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
The number of specimens testing positive for influenza decreased together with the number of samples tested due to relatively low reporting rate by the countries in western part of the region caused by holidays this week.
Overall, a total of 386 specimens tested positive for influenza in week 51/2012: 275 were type A and 111 were type B.
Of the influenza A viruses, 74 were subtyped: 38 as A(H3N2) and 41 as A(H1N1)pdm09 (Fig. 1).
Since week 40/2012 influenza A and influenza B viruses have been detected in similar proportions, 2295 influenza viruses from sentinel and non-sentinel sources have been typed: 1379 (60%) were influenza A and 916 (40%) influenza B.
Of the influenza A viruses 794 were subtyped: 415 (52%) as A(H3N2) and 379 (48%) as A(H1N1)pdm09 (Fig 2).
During week 51/2012, Denmark reported influenza A as the dominant virus type while Belgium, Luxembourg and Spain reported influenza B as dominant type. France reported both influenza A and B as the dominant type (Map 1). It is still too early to assess which influenza viruses will dominate this season as the number of detections remains relatively low.
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, 54 influenza viruses characterized antigenically by 6 countries (Denmark, the United Kingdom (England), Germany, Latvia, Portugal, Romania) 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 91 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 60 viruses for susceptibility to the neuraminidase inhibitors oseltamivir and zanamivir.
The 26 influenza A(H3N2) viruses, 27 A(H1N1)pdm09 viruses and 7 influenza B viruses showed susceptibility to oseltamivir and zanamivir.
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)
Consultation rates for ILI and ARI remain at usual for this time of the year levels throughout the WHO European Region with only 1 country (France) reporting medium intensity (Map 2). Three countries; France, Netherlands and the United Kingdom (England) reported regional or widespread circulation of influenza (Map 3), while only 11 of 30 reported increasing trends (Map 4).
The influenza-positivity rate among ILI and ARI cases from sentinel sources remain at similar level as during the previous week with less specimens tested for influenza: 121 (18%) of 662 specimens tested positive for influenza this week (Fig. 5).
Of the 662 specimens from sentinel sources, 69 tested positive for influenza A and 52 for influenza B (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.
Hospital surveillance for SARI
Hospitalizations due to SARI remain stable and at pre-season levels in the 9 countries reporting this week (Armenia, Belarus, Georgia, Kazakhstan, Kyrgyzstan, Republic of Moldova, the Russian Federation, Serbia and Ukraine) with most cases reported in the age group 0–4 years (Fig. 7).
To date, only few influenza detections have been reported by the hospitals participating in SARI surveillance, similar to the situation in outpatient surveillance in these countries. In week 51, 1 case tested positive among 132 specimens collected from hospitalized SARI cases in 7 countries (Belarus, Georgia, Kazakhstan, Kyrgyzstan, the Russian Federation, Serbia and Ukraine); with Kyrgyzstan reported 1 SARI case positive for influenza B.
Since week 40/2012, 1493 SARI specimens have been collected and tested for influenza with only 12 influenza detections among those cases (Fig. 8b). Click here for a detailed overview in table format.
For the countries reporting to the European Centre for Disease Prevention and Control (ECDC) on severe influenza in hospitals, no cases were reported positive for influenza this week.
For the surveillance of confirmed hospitalized influenza see the Weekly Influenza Surveillance Overview (WISO) at European Centre for Disease Prevention and Control web site.
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)
- Denmark: The data from Denmark week 51 is not national as data from the regions are missing due to the holidays. The numbers will be updated when we have the data. However; based on other reports there has been an increase in ILI consultations during the holidays and the dominant type is influenza A H3N2.
- Republic of Moldova: This 51st Influenza Surveillance week were tested 20 specimens: 1 sample was positive for RNA hRSV and 1 sample - for RNA Parainfluenza type 3.