1 Feb 2013

EuroFlu - Weekly Electronic Bulletin - Week 4 : 21/01/2013-27/01/2013 - 01 February 2013, Issue No. 473 (edited)

[Source: EuroFlu, full page: (LINK). Edited.]

EuroFlu - Weekly Electronic Bulletin - Week 4 : 21/01/2013-27/01/2013 - 01 February 2013, Issue No. 473

Levels of influenza activity indicate a west-to-east progression across Europe

 

Summary, week 4/2013

  • Consultation rates for influenza-like illness (ILI) and/or acute respiratory infection (ARI) are increasing in most countries in the WHO European Region.
  • In line with observations in previous seasons, influenza activity appears to be migrating from west to east, with countries in the west possibly having reached peak activity while those in the east show slow increases.
  • Influenza A(H1N1)pdm09 remains predominant with co-circulation of influenza A(H3N2) and type B viruses.
  • The proportion of samples from sentinel and non-sentinel sources testing positive for influenza reached its highest level (49%) so far this season.
  • The proportion of severe acute respiratory infection (SARI) cases testing positive for influenza continued to increase, mainly owing to influenza A.

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, the number of specimens testing positive for influenza in the Region increased in week 04/2013. Armenia was the only country to report no specimens testing positive for influenza up to this week. Overall, a total of 4699 specimens tested positive for influenza in week 04/2013, with 3453 (73%) testing positive for influenza A, similarly to the previous week (Fig. 1).

IIn week 04/2013, influenza A(H1N1)pdm09 viruses continued to dominate: of 2160 influenza A viruses subtyped, 1739 (81%) were A(H1N1)pdm09 while only 421 (19%) were A(H3N2) (Fig. 2a). This presents a very different picture from the 2011/2012 influenza season, when A(H1N1)pdm09 detections were rare, but is similar to the 2010/2011 season.

In the 32 countries testing 20 or more sentinel specimens, influenza positivity ranged from 0% to 95.4%, with a median of 46% (mean: 45%).

Since the beginning of the season (week 40/2012), 22 029 influenza viruses from sentinel and non-sentinel sources have been typed: 15 307 (69%) were influenza A and 6 722 (31%) influenza B (Fig. 2b).

Of the influenza A viruses, 9163 were subtyped: 6458 (70%) as A(H1N1)pdm09 and 2705 (30%) as A(H3N2). In addition, the lineage for 999 influenza B viruses has been determined since week 40/2012: 897 (90%) belonged to the B/Yamagata lineage and 102 (10%) to B/Victoria.

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Circulation of influenza viruses in week 04/2013 remained diverse and similar to the previous week across the Region.

Influenza A (mainly A(H1N1)pdm09) was reported as the dominant virus in an increasing number of countries in northern, eastern and central Europe, and Turkey, while influenza B was reported as the dominant virus in some countries in the southern and western parts of the Region (Map 1). Between these areas, co-circulation of A(H1N1)pdm09, A(H3N2) and influenza B was reported.

 

Virus strain characterizations

For 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 vaccines (see more at WHO web site).

Since week 40/2012, 1149 influenza viruses characterized antigenically by 12 countries (Denmark, the United Kingdom (England), Germany, Greece, Latvia, Portugal, Romania, the Russian Federation, Scotland, Slovakia, Slovenia, Switzerland) corresponded with the viruses recommended by WHO for inclusion in the current northern hemisphere seasonal influenza vaccine (Fig. 3).

12 countries (Austria, Belgium, Denmark, Finland, Germany, Greece, Norway, Portugal, Scotland, Spain, Sweden, Switzerland) have characterized 318 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.

Both A(H1N1)pdm09 and A(H3N2) viruses have evolved to fall into a number of different genetic groups, which are all antigenically similar to their vaccine viruses, A/California/7/2009 and A/Victoria/361/2011, respectively.

Influenza B viruses of the B/Victoria/2/87 and the B/Yamagata/16/88 lineages are co-circulating with the clear dominance of the B/Yamagata lineage viruses this season. Influenza B viruses of the B/Victoria lineage all fall within the B/Brisbane/60/2008 clade and are antigenically indistinguishable. B/Yamagata lineage viruses in circulation clearly fall into two distinct genetic clades, represented by B/Estonia/55669/2011 (Clade 2) and B/Wisconsin/1/2010 (Clade 3) respectively. Viruses in these clades can be distinguished antigenically from each other, but the antigenic differentiation of these clades is not clear-cut as post-infection ferret antisera raised against clade 2 viruses are more clade-specific than are antisera raised against clade 3 viruses. Nevertheless, viruses within these clades remain antigenically similar to the current vaccine virus.

 

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 262 viruses for susceptibility to the neuraminidase inhibitors oseltamivir and zanamivir.

The 95 influenza A(H3N2) and 67 influenza B viruses showed susceptibility to both drugs.

Of the 100 A(H1N1)pdm09 viruses tested, 99 showed susceptibility to both drugs and 1 virus carrying the neuraminidase H275Y amino acid substitution, causing resistance to oseltamivir, was detected in the Netherlands in a hospitalized immunocompromised patient exposed to oseltamivir through treatment (see Country comments for more details).

The 14 influenza A(H3N2) and 10 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)

ILI and ARI consultation rates continue to increase in the eastern part of the Region (Map 4), but mainly with reported low intensity levels (Map 2).

In Norway, Poland and the United Kingdom (Northern Ireland), consultation rates for ILI and ARI are decreasing (Map 4), along with the numbers of specimens testing positive for influenza (see table and graphs for individual country data). Most of the countries across the Region reported regional or widespread circulation of influenza for week 04/2013 (Map 3).

Of the 20 countries that have established epidemic thresholds, 4 (Kazakhstan, Romania, Serbia and Ukraine) reported ILI/ARI consultation rates below their national threshold levels.

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The number of specimens testing positive for influenza from sentinel outpatient clinics reached the highest level so far this season. Overall, 2855 specimens were tested, of which 1391 (49%) were positive for influenza in week 04/2013 (Fig. 5).

Of the 1391 influenza-positive specimens from sentinel sources, influenza A was detected in 59% (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

The proportion of respiratory specimens from patients with SARI testing positive for influenza has continued to rise since week 01/2013 (Fig. 7), in line with increasing influenza activity in countries reporting on SARI hospitalizations. Overall, the majority of countries reported cases mainly in the group aged 0–4 years, (see Country data and graphsfor individual country data).

For week 04/2013, 11 countries (Belarus, Belgium, Georgia, Kazakhstan, Kyrgyzstan, the Republic of Moldova, Romania, the Russian Federation, Serbia, Slovakia and Ukraine) reported 40 influenza detections among 223 specimens tested, 70% of which (28) were influenza A (Fig. 8a). Since week 40/2012, 2553 SARI specimens have been collected and tested for influenza. Click here for a detailed overview in table format.

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Among the countries reporting on hospitalization of severe influenza cases to the European Centre for Disease Prevention and Control (ECDC), 71 such cases were reported for week 04/2013.

This reflects the continued higher 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) atEuropean Centre for Disease Prevention and Control web site.

 

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 04/2013 data from 13 countries, or regions within countries, shows no substantial excess all-because mortality as yet this season. For more information about the EUROMOMO mortality monitoring system please click here)

'Erratum: The ILI rates presented for Hungary are not correct. The actual ILI rates are 136 consultations per 100 000 population '.

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Country comments (where available)

  • Czech Republic: Up to end of week 4/2013 a cumulative total of 196 severe influenza patients with laboratory-confirmed influenza were reported by intensive and resuscitation care units including 40 deaths
  • Netherlands: 'In the Netherlands, a hospitalised immunocompromised patient was identified carrying an oseltamivir resistant A(H1N1)pdm09 virus with the H275Y amino acid substitution. This resistant variant emerged during oseltamivir therapy and was detected shortly after oseltamivir was stopped and before zanamivir therapy was started. The patient was also treated with antibiotics for pneumoniae due to Haemophilus influenzae, thereof improved rapidly and was discharged 20 days after onset of respiratory symptoms.'
  • Republic of Moldova: This 4th sentinel surveillance week, totally, were tested 27 samples: 3 samples were positive for A(H1N1)pdm; 1 was positive for A(H3N2); 4 positive for Influenza virus type B and 1 sample was positive for both ARN Influenza virus A(H1N1)pdm and Influenza virus type B.
  • Slovenia: By the side of influenza positives, in this season we are observing persistance of high proportion of RSV positive specimens.

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