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FINLAY ALBARRAN
MEDICAL INSTITUTE
INFLUENZA (19): EUROPE UPDATE
Date: Fri 4 Mar 2011 Source: WHO Regional Office for Europe, EuroFlu: Weekly Electronic Bulletin [edited] <http://www.euroflu.org/cgi-files/bulletin_v2.cgi>
Influenza activity continues, but declines in many countries in the WHO European Region
Summary ------- - Clinical influenza-like illness (ILI) and acute respiratory infection (ARI) activity are decreasing in 24 countries of the [53 in the] Region. - According to sentinel surveillance, severe acute respiratory infection (SARI) shows declining trends in some countries, but remains above pre-season levels. - 39 percent of sentinel specimens from patients with ILI and/or ARI, and 56 percent of specimens from sentinel SARI patients tested positive for influenza. - Pandemic influenza A(H1N1) 2009 and influenza B continue to co-circulate in the Region.
Current situation -- week 8/2011 [21-27 Feb 2011] ------------------------------------------------- During week 8/2011, ILI or ARI consultation rates decreased in all age groups in 24 of the 35 countries reporting clinical data. Among 38 countries reporting on the geographical spread of influenza, most reported either widespread (15) or regional (7) activity, while 16 reported either sporadic or local activity. Only 5 countries reported high-intensity influenza activity (compared with 9 countries last week [14-20 Feb 2011]), while 21 countries reported medium intensity and 11 countries, low intensity. The impact of influenza on health care systems was low in 14 and moderate in 10 of the 24 countries reporting on this indicator.
Data from sentinel hospital-based surveillance for SARI were received from 9 countries (Armenia, Georgia, Kazakhstan, Kyrgyzstan, Romania, the Republic of Moldova, the Russian Federation, Serbia, and Ukraine). Sentinel SARI hospitalizations have decreased substantially in Georgia, Kazakhstan, Kyrgyzstan, and the Russian Federation, concurrent with overall declines in outpatient ARI or ILI consultation rates in these 4 countries. In Romania, Serbia, and Ukraine, SARI hospitalizations increased, as did the percentage of SARI specimens testing positive for influenza. Among countries testing 10 or more sentinel SARI specimens, the percentage testing positive for influenza ranged from 40 percent in Kazakhstan to 67 percent in Ukraine with a median of 65 percent (mean: 53 percent). Further information on the sentinel SARI surveillance systems represented in the EuroFlu bulletin can be found in the "Overview of sentinel SARI systems in EuroFlu".
Virological situation - week 8/2011 [21-27 Feb 2011] ---------------------------------------------------- Pandemic influenza A(H1N1) 2009 was reported to be dominant in 7 countries and co-dominant with influenza B in 16 countries. Influenza B was dominant in 7 countries.
Sentinel physicians collected 1611 respiratory specimens, of which 621 (39 percent) were positive for influenza virus: 273 (44 percent) were influenza A and 348 (56 percent) were influenza B. Of the influenza A viruses, 243 were subtyped: 224 (92 percent) as pandemic A(H1) and 19 (8 percent) as A(H3). In the 20 countries testing 20 or more sentinel specimens, influenza positivity ranged from 3 percent to 94 percent, with a median of 39 percent (mean: 39 percent). In addition, 3639 non-sentinel specimens were reported positive for influenza: 2538 (70 percent) influenza A and 1101 (30 percent) influenza B. Of the influenza A viruses, 2110 were subtyped: 2088 (99 percent) as pandemic A(H1) and 22 (1 percent) as A(H3).
Out of 226 sentinel SARI specimens collected during week 8/2011 (data from 8 countries), 126 (56 percent) tested positive for influenza: 65 (52 percent) were influenza A; 61 (48 percent) were influenza B. Of the influenza A viruses, 41 were subtyped: 39 (95 percent) as pandemic A(H1), and 2 (5 percent) as A(H3).
Cumulative virological update - weeks 40/2010 - 8/2011 [4 Oct 2010-27 Feb 2011] ---------------------------------------------------------------------- A total of 69 762 influenza virus detections were reported during this period, of which 50 098 (72 percent) were influenza A and 19 664 (28 percent) were influenza B. Of the influenza A viruses, 38 790 were subtyped: 37 395 (96 percent) as pandemic A(H1), 1 394 (4 percent) as influenza A(H3) and 1 as influenza A(H1).
From week 40/2010 [4-10 Oct 2010] to week 8/2011 [21-27 Feb 2011], 1057 out of 3626 sentinel SARI specimens (29 percent) tested positive for influenza. Of these influenza viruses, 526 (50 percent) were influenza A and 531 (50 percent) influenza B. Of the influenza A viruses, 357 were subtyped: 331 (93 percent) as pandemic A(H1) and 26 (7 percent) as influenza A(H3).
Since week 40/2010, 2771 influenza viruses have been characterized antigenically: 1478 were A(H1) pandemic A/California/7/2009 (H1N1)-like; 1107 were B/Brisbane/60/2008-like (B/Victoria/2/87 lineage); 102 were A(H3) A/Perth/16/2009 (H3N2)-like; 83 were B/Florida/4/2006-like (B/Yamagata/16/88 lineage); and 1 was B/Bangladesh/3333/2007-like (B/Yamagata/16/88 lineage). Based on the genetic characterization of 384 influenza viruses, 164 belonged to the pandemic A/California/7/2009 A(H1N1) clade; 8 belonged to the pandemic A/Christchurch/16/2010 A(H1) clade; 38 belonged to the pandemic A/Hong Kong/2213/2010 A(H1) clade; 34 were reported as A(H1) pandemic not attributed to group category but belonging to the recently emerged A/England/142/2010 subgroup characterized by S185T substitution in the HA; 9 belonged to the A(H3) clade represented by A/Perth/16/2009; 6 belonged to the A(H3) clade represented by A/Victoria/208/2009; 20 belonged to the subgroup represented by A/Hong Kong/2121/2010 in the A/Victoria/208/2009 A(H3) clade; 9 belonged to the B/Bangladesh/3333/2007 clade (Yamagata lineage); and 96 to the B/Brisbane/60/2008 clade (Victoria lineage).
Since week 40/2010, 7 countries (Germany, Ireland, Italy, Norway, Spain, Switzerland, and the UK) have screened 990 viruses for susceptibility to the neuraminidase inhibitors oseltamivir and zanamivir. The UK analysed most of the viruses screened (671). Out of the 924 pandemic A(H1N1) viruses that were tested, 892 were sensitive to both inhibitors and 32 viruses (3.5 percent) carried the NA H275Y mutation. These 32 viruses were resistant to oseltamivir but remained sensitive to zanamivir. 3 influenza A(H3N2) viruses were tested and found to be sensitive to both inhibitors. All of the 62 influenza B viruses tested for susceptibility to oseltamivir and the 63 tested for susceptibility to zanamivir were found to be sensitive. All 115 pandemic influenza A(H1N1) 2009 viruses and 2 A(H3N2) viruses that were screened for susceptibility to adamantanes were found to be resistant.
Comment ------- Clinical ILI and ARI consultation rates continue to decline throughout most parts of the WHO European Region with most countries reporting medium activity. A few countries, however, observe persisting and increasing clinical outpatient activity. The percentage of sentinel specimens testing positive for influenza is declining overall, but remains high in several countries. Whereas pandemic influenza A(H1N1) 2009 and influenza B currently co-dominate in northern and western Europe, pandemic influenza A(H1N1) 2009 is the dominant virus in the central and eastern parts of the Region.
Sentinel surveillance for SARI indicates that SARI hospitalizations are declining in the south eastern part of the Region, while some countries in central Europe are observing increasing trends. Prior to seasonal increases in influenza activity, a relatively large portion of sentinel SARI hospitalizations occurred in the group aged 0-4. With increases in influenza activity, however, particularly that associated with circulation of pandemic A(H1N1) 2009 viruses, there have been associated increases in the relative proportion of SARI hospitalizations in older children, young adults and adults.
[In brief: only 5 countries reported high-intensity influenza activity compared with 9 countries in the previous week (14-20 Feb 2011], The percentage of sentinel specimens testing positive for influenza is declining overall.
Whereas pandemic influenza A(H1N1) 2009 and influenza B are currently co-dominant in northern and western Europe, pandemic influenza A(H1N1) 2009 is the dominant virus in the central and eastern parts of the Region.
Most pandemic influenza A(H1N1) 2009 belonged to one of 3 distinct clades with the exception of 34 isolates belonging to the recently emerged subgroup in England characterized by an S185T substitution in HA.
The EuroFlu website features an interactive map presenting qualitative indicators of influenza activity (intensity, trend, geographical spread, and impact) and the dominant virus as assessed by each of the countries. This information can be accessed by clicking on the individual countries in the map and readers are recommended to make use of this facility. - Mod.CP]
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