[Source: EuroFlu.org, full page: (LINK). Edited.]
EuroFlu - Weekly Electronic Bulletin - Week 48 : 26/11/2012-02/12/2012 - 07 December 2012, Issue N° 465
Sporadic influenza detections largely restricted to countries in western Europe
Summary, week 48/2012
Influenza activity in the WHO European Region remains at a pre-season level, with countries reporting sporadic detections of influenza viruses predominantly in western Europe.
Influenza B was detected in more than half of the cases testing positive for influenza this week.
The number of hospitalizations due to severe acute respiratory infection (SARI) remains stable, with 1 case related to influenza A reported this week.
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
Overall, a total of 187 specimens tested positive for influenza in week 48/2012: 90 were type A and 97 were type B.
Of the influenza A viruses, 39 were subtyped: 17 as A(H3N2) and 22 as A(H1N1)pdm09 (Fig. 1).
Based on the data reported by countries this week, there is currently no clear pattern of circulation or dominance of influenza A and influenza B viruses in the Region (Map 1).
Since week 40/2012, 868 influenza viruses from sentinel and non-sentinel sources have been typed: 509 (59%) were influenza A and 359 (41%) influenza B.
Of the influenza A viruses 298 were subtyped: 170 (57%) as A(H3N2) and 128 (43%) as A(H1N1)pdm09 (Fig 2).
Owing to the low number of viruses detected in week 48/2012, only 1 country (United Kingdom) reported a dominant virus: influenza A and B in Scotland and influenza B in Wales, as shown on the map.
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, 4 countries (Denmark, the United Kingdom (England), Germany, Romania) have characterized 32 influenza viruses antigenically (Fig. 3). 7 countries (Denmark, Finland, Germany, Norway, Portugal, Spain, Sweden) have characterized 48 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, 4 countries (Germany, the Netherlands, Sweden and the United Kingdom) have screened 34 viruses for susceptibility to the neuraminidase inhibitors oseltamivir and zanamivir.
All 9 influenza A(H3N2), 21 A(H1N1)pdm09 viruses and 4 influenza B viruses showed susceptibility to oseltamivir and zanamivir.
The 7 influenza A(H3N2) and 2 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 continue to be low (Map 2), as usual for this time of the year, throughout the WHO European Region.
24 out of 43 countries reported no geographic spread (Map 3), while 8 of 44 reported increasing trends (Map 4).
Only 1 country among 18 that have established epidemic thresholds (the Russian Federation) reported that ILI/ARI consultation rates had reached the national threshold level.
The influenza-positivity rate among ILI and ARI cases from sentinel sources increased slightly, along with the number of specimens tested: 6.4% of 761 specimens tested were influenza positive (Fig. 5).
Of 761 specimens from sentinel sources, 17 tested positive for influenza A and 32 for influenza B (Fig. 6a). Fig. 6b gives a detailed overview of cumulative influenza virus detections by type and subtype since week 40/2012.
Hospital surveillance for SARI
Sentinel SARI hospitalization rates are still low and at pre-season levels, with most cases occurring in the group aged 0–4 years (Fig. 7).
10 out of 11 reporting countries (Armenia, Belarus, Georgia, Kazakhstan, Kyrgyzstan, Republic of Moldova, Romania, Russian Federation, Serbia and Ukraine) reported hospitalizations due to SARI.
Reported by Ukraine, 1 SARI case was positive for influenza A(H1)pdm09.
A total of 137 specimens was collected from hospitalized SARI cases in 8 countries (Armenia, Belarus, Georgia, Kazakhstan, Kyrgyzstan, Russian Federation, Romania and Ukraine). Fig. 8b gives a detailed overview of cumulative influenza virus detections by type and subtype since week 40/2012.
For the countries reporting to the European Centre for Disease Prevention and Control (ECDC) on severe influenza in hospitals, no positive cases were reported 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)
- Norway: Moderate and increasing number of influenza virus detections. A(H1)pdm09, A(H3) and B Yamagata lineage viruses are circulating sporadically, with influenza B (Yamagata lineage) slightly more predominant than the others.
- Republic of Moldova: In the 48th week 17 sentinel samples were tested: 1 sample was positive for both DNA Adenovirus and RNA Parainfluenza virus type 3; 1 sample was positive for DNA Adenovirus and 4 samples positive for RNA hRSV. Influenza viruses were not detected in any of the tested specimens.
- Spain: From week 40/2012 520 sentinel specimens have been tested for influenza. From them 15 were positive for influenza B virus and 1 for influenza C. No viruses A have been identified so far in Spain. There is a sporadic circulation of B influenza virus and 7 of them has been genetically characterized as B Yamagata lineage virus (6 belonged to B/Estonia/55669/2011 and 1 belonged to B/Wisconsin/1/2010)