[Source: EuroFlu, full page: (LINK). Edited.]
EuroFlu - Weekly Electronic Bulletin - Week 49 : 03/12/2012-09/12/2012 - 14 December 2012, Issue N° 466
Sporadic influenza detections in the WHO European Region
Summary, week 49/2012
- Influenza activity in the WHO European Region remains at a low level, with growing numbers of countries in different parts of the Region reporting sporadic detections of influenza viruses.
- Similarly to last week, influenza B was detected in more than half of the cases from sentinel sources testing positive for influenza.
- The number of hospitalizations due to severe acute respiratory infection (SARI) remains stable, with 3 cases 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 280 specimens tested positive for influenza in week 49/2012: 152 were type A and 128 were type B.
Of the influenza A viruses, 86 were subtyped: 45 as A(H3N2) and 41 as A(H1N1)pdm09 (Fig. 1).
Since week 40/2012, 1177 influenza viruses from sentinel and non-sentinel sources have been typed: 681(58%) were influenza A and 496 (42%) influenza B.
Of the influenza A viruses 421 were subtyped: 240 (57%) as A(H3N2) and 181 (43%) as A(H1N1)pdm09 (Fig 2).
Owing to the growing number of viruses detected in week 49/2012, 3 countries reported influenza A as the dominant type(Denmark, Slovenia and Sweden), and 1 country – the United Kingdom (Wales and Northern Ireland) reported influenza B as dominant, as shown on Map 1.
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, 5 countries (Denmark, the United Kingdom (England), Germany, Portugal, Romania) have characterized 43 influenza viruses antigenically (Fig. 3). 6 countries (Denmark, Finland, Germany, Norway, Portugal, Sweden) have characterized 63 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.
This corresponds with the viruses recommended by WHO for inclusion in the current northern hemisphere seasonal influenza vaccine.
Monitoring of susceptibility to antiviral drugs
Since week 40/2012, 6 countries (Germany, Norway, the Netherlands, Spain, Sweden and the United Kingdom) have screened 54 viruses for susceptibility to the neuraminidase inhibitors oseltamivir and zanamivir.
The 22 influenza A(H3N2) viruses, 25 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 low and typical for this time of the year throughout the WHO European Region (Map 2); 18 out of 40 countries reported no geographic spread (Map 3), while 14 of 40 reported increasing trends (Map 4).
Of the 18 countries that have established epidemic thresholds, 2 (Albania and the Russian Federation) reported ILI/ARI consultation rates above their national threshold levels.
The influenza-positivity rate among ILI and ARI cases from sentinel sources again showed a slight increase, along with the number of specimens tested: 81 (8.5%) of 954 specimens tested positive for influenza this week (Fig. 5).
Of 954 specimens from sentinel sources, 39 tested positive for influenza A and 42 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
Sentinel SARI hospitalization rates are stable, with most cases occurring in the group aged 0–4 years (Fig. 7). Of 11 reporting countries, 9 (Belarus, Georgia, Kazakhstan, Kyrgyzstan, the Republic of Moldova, Romania, the Russian Federation, Serbia and Ukraine) reported hospitalizations related to SARI.
The Russian Federation reported 3 SARI cases positive for influenza A(H3N2).
A total of 130 specimens has been collected from hospitalized SARI cases in 9 countries (Belarus, Georgia, Kazakhstan, Kyrgyzstan, the Republic of Moldova, Romania, the Russian Federation, Serbia and Ukraine). Fig. 8b gives a detailed overview of cumulative influenza virus detections by type and subtype since week 40/2012. 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, 1 case was reported positive for influenza B 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: This week none of the 20 sentinel specimens were positive for Influenza Viruses. Only 2 samples were positive for DNA Adenovirus.