Summary. Primary care data. Week 49/2014. Season

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1 Summary Week 49/2014 In week 49/2014, influenza activity remained low across the WHO European Region. Twenty countries reported sporadic influenza activity and nine reported increasing trends in consultations for influenza-like illness (ILI) and/or acute respiratory infection (ARI). Of the 848 specimens tested from sentinel ILI and ARI patients from 35 countries, 34 (4%) from 14 countries tested positive for influenza virus. At present, the predominant influenza virus subtype circulating is A(H3N2). Two countries reported a total of 14 hospitalized laboratory-confirmed influenza cases that were admitted to intensive care units, similar to that in the previous week. The characterization data in Europe show the same differences between most of the circulating A(H3N2) viruses and the virus used in the influenza vaccine, as also reported by the United States Centers for Disease Control and Prevention (CDC) ( Season Although an increasing number of countries reported sporadic influenza virus detections, there is no indication that the influenza season has started in the Region, which is normal for this time of year. No indications of increased mortality have been reported through the European monitoring of excess mortality for public health action project (EuroMOMO Primary care data Thirty-nine of the 40 countries submitting data on qualitative indicators reported low intensity of influenza activity for week 49/2014; one (Malta) reported medium intensity. Twenty countries reported sporadic influenza activity, while the Netherlands and the United Kingdom (England) reported regional spread. Nine countries reported increasing influenza activity, while the remainder reported stable or decreasing trends: Bulgaria, Lithuania, Luxembourg, Malta, Poland, Portugal, the Republic of Moldova, the United Kingdom (England and Northern Ireland) and Uzbekistan. Increasing ILI and ARI rates were observed in most countries. Only in Estonia did the rate cross the epidemic threshold, but no specimens positive for influenza virus were reported. Israel reported a strong increase in ILI activity, with 13% of sentinel specimens testing positive for influenza. In week 49/2014, 848 sentinel specimens were tested across 31 countries, with 34 (4%) in 14 countries being positive for influenza virus; 27 were of type A and seven of type B. Eighteen of the influenza A viruses were subtyped; six were A(H1N1)pdm09 and 12 were A(H3N2). The lineage of three of the seven B viruses was determined; all were of the B/Yamagata lineage. 1

2 Flu News Europe Joint ECDC-WHO/Europe weekly influenza update Over the first 10 weeks of the weekly reporting period for the influenza season, influenza viruses have been detected in 170 (3%) of 6348 sentinel specimens: 111 (65%) were positive for type A influenza virus and 59 (35%) for type B. Of the A viruses, 67 (60%) were A(H3N2), 18 (16%) A(H1N1)pdm09 and 26 (24%) unsubtyped (Fig. 1). The lineage of 13 B viruses was determined: two were B/Victoria lineage and 11 B/Yamagata lineage. Among sentinel specimens collected in week 49/2014 and tested for respiratory syncytial virus (RSV), 35 across six countries were positive, and 855 specimens from other sources were found to be positive in 11 countries. This represents a slight increase from the previous week. Fig. 1. Number and proportion of sentinel specimens positive for influenza virus, by (sub)type and week of specimen collection, weeks 40 49/2014 Data from other sources In addition, 161 (2%) of 7444 specimens from non-sentinel sources (mainly from hospital laboratories, not primary care) that were collected in week 49/2014 tested positive for influenza virus: 128 were type A and 33 type B. Fifty-five type A influenza viruses were subtyped: 12 as A(H1N1)pdm09 and 43 as A(H3N2). Since week 40/2014, 802 (1%) of specimens from non-sentinel sources have tested positive for influenza virus: 567 (71%) were type A and 235 (69%) type B. Of the type A viruses, 294 were subtyped: 62 (21%) as A(H1N1)pdm09 and 232 (79%) as A(H3N2) (Fig. 2). The lineage of 42 influenza B viruses was determined: all were of the B/Yamagata lineage. 2

3 Joint ECDC-WHO/Europe weekly influenza update Flu News Europe Fig. 2. Number of non-sentinel specimens positive for influenza virus, by (sub)type and week of specimen collection, weeks 40 49/2014 Hospital data For week 49/2014, Ireland reported one hospitalized laboratory-confirmed influenza case. Spain and the United Kingdom reported 14 hospitalized laboratory-confirmed influenza cases, which were admitted to intensive care units (ICU): 12 cases were diagnosed with influenza A and two with influenza B. Since week 40/2014, three countries (Ireland, Spain and the United Kingdom) have reported a total of 47 laboratory-confirmed, hospitalized influenza cases. Of these, 46 were admitted to ICUs: 41 cases reported by the United Kingdom and five by Spain. Of these, 37 were positive for influenza A virus (with seven subtyped as A(H3N2)), and nine for influenza B virus. Spain reported one fatal hospitalized laboratoryconfirmed influenza case that had not been admitted to an ICU. Virus characteristics Since week 40/2014, 21 antigenic characterizations of influenza viruses have been reported: seven A(H1N1)pdm09 were A/California/7/2009-like; 10 A(H3N2) were A/Texas/50/2012-like; three were B/Massachusetts/02/2012-like and one was B/Phuket/3073/2013-like (all B/Yamagata/16/88-lineage). Forty-three viruses have been genetically characterized: five belonging to A(H1N1)pdm09 6B genetic subgroup represented by A/SouthAfrica/3626/2013; six belonging to the A(H3N2) A/Texas/50/2012 3C subgroup, 21 to the A(H3N2) A/HongKong/5738/2014 3C.2a subgroup, four to the A(H3N2) A/Switzerland/ /2013 3C.3a subgroup, two to the A(H3N2) A/Samara/73/2013 3C.3 subgroup, and five to the B/Phuket/3073/2013 clade (clade 3). Viruses that have been characterized to date, by laboratories reporting to the European Surveillance System (TESSy), as A(H1N1)pdm09 and influenza type B are similar to those included in the current vaccines recommended by WHO. Of the genetically characterized A(H3N2) viruses, eight (six A/Texas/50/2012 subgroup 3C.1 and two A/Samara/73/2013 3C.3) are in genetic groups containing viruses that have antigenic properties similar to the vaccine virus, but 25 (21 A/Hong Kong/5738/2014 3C.2a and four A/Switzerland/ /2013 3C.3a) are in genetic groups containing viruses that show antigenic drift from the vaccine virus. In summary, 76% of the genetically characterized A(H3N2) viruses are in subgroups containing antigenic drift variants compared to A/Texas/50/2012 (the vaccine component for the northern hemisphere season). 3

4 Flu News Europe Joint ECDC-WHO/Europe weekly influenza update This indicates a situation in Europe similar to that reported by CDC for week 48/2014 ( with the majority of A(H3N2) viruses showing mismatches with the current component of the seasonal influenza vaccine. The September 2014 virus characterization report of the European Centre for Disease Prevention and Control (ECDC) offers more details on viruses with collection dates since 31 January2014. Twenty-two influenza A(H3N2) viruses, nine influenza A(H1N1)pdm09 viruses and one influenza B virus underwent phenotypic or genotypic testing for neuraminidase inhibitor susceptibility. None showed evidence of reduced oseltamivir and zanamivir susceptibility. Eighteen A(H3N2) viruses were tested for M2 ion channel blocker susceptibility (adamantanes); all were resistant due to the S31N amino acid substitution in the M2 protein. System description Influenza surveillance in the European Region is based on nationally organized networks of primary care physicians, mostly general practitioners (GPs), covering at least 1 5% of the population in their countries. Depending on the country, physicians report the weekly number of patients seen with ILI, ARI or both, to the national focal point for influenza surveillance. Primary care surveillance for influenza in the Region is mostly based on sentinel systems (i.e. data are collected and reported only from selected facilities), although some countries collect data on ILI or ARI from all health facilities in the country (universal surveillance). A subset of specimens from sentinel ILI and ARI patients are tested for influenza and RSV infection. In addition, some countries, mainly in the eastern part of the European Region, are conducting sentinel surveillance for hospitalized cases presenting with severe acute respiratory infection (SARI) according to standard case definitions. Depending on the country, all or a subset of SARI patients are tested for influenza virus infection. A subset of countries reports laboratory-confirmed influenza positive hospitalized cases every week. Case definitions, populations under surveillance and data formats differ among these countries. Most countries also report on additional semi-quantitative indicators of intensity, geographic spread and trend of influenza activity at the national level. Table 1 shows the types of surveillance carried out by countries in the European Region. National influenza centres (NICs) are institutions designated by countries ministries of health and recognized by WHO to participate in the work of the WHO Global Influenza Surveillance and Response System. NICs receive respiratory specimens from a range of sources in their countries and provide virological data on characteristics of circulating influenza viruses according to influenza type and subtype (A(H3N2) and A(H1N1)pdm09) or lineage (B/Victoria or B/Yamagata). In addition, influenza viruses are assessed each season for their antigenic and genetic characteristics, to determine the extent of their similarity to the viruses included in the seasonal influenza vaccine. The prevalence of mutations that affect pathogenicity or are associated with reduced susceptibility to antiviral drugs is also determined. Further, susceptibility to neuraminidase inhibitor antivirals is assessed by phenotypic tests. Data are reported from the national level to TESSy on a weekly basis during the influenza surveillance season (week 40 to week 20 in the following year). Intensity of influenza activity is described as: low = no activity or activity at baseline level; medium = usual levels of activity; high = levels of activity higher than usual; very high = exceptionally high levels of activity. Geographic spread is described as: no activity = either no laboratory-confirmed cases, or no evidence of increased or unusual respiratory disease activity; sporadic = isolated cases of laboratory-confirmed influenza infection; localized = laboratory-confirmed influenza infection limited to one administrative unit in the country (or reporting site) only; 4

5 Joint ECDC-WHO/Europe weekly influenza update Flu News Europe regional = laboratory-confirmed influenza infection appearing in multiple but under 50% of the administrative units of the country (or reporting sites); widespread = laboratory-confirmed influenza infection appearing in 50% or more of the administrative units of the country (or reporting sites). Trend is described as: increasing = evidence that the level of respiratory disease activity is increasing compared with the previous week; stable = evidence that the level of respiratory disease activity is unchanged compared with the previous week; decreasing = evidence that the level of respiratory disease activity is decreasing compared with the previous week. Dominant type is assessed based on data from sentinel and non-sentinel sources. Table 1. Types of surveillance carried out by countries in the WHO European Region Country Primary care surveillance Hospital surveillance ILI ARI SARI Laboratory-confirmed influenza Albania Armenia 1 Austria Azerbaijan Belarus Belgium Bosnia and Herzegovina Bulgaria Croatia 2 Cyprus Czech Republic Denmark Estonia Finland 2 France Georgia Germany Greece 5

6 Flu News Europe Joint ECDC-WHO/Europe weekly influenza update Country Primary care surveillance Hospital surveillance Hungary Iceland ILI ARI SARI Laboratory-confirmed influenza Ireland Israel Italy Kazakhstan Kyrgyzstan Latvia Lithuania Luxembourg Malta Montenegro Netherlands Norway Poland Portugal Republic of Moldova Romania Russian Federation Serbia Slovakia Slovenia Spain Sweden Switzerland Tajikistan 6

7 Joint ECDC-WHO/Europe weekly influenza update Flu News Europe Country Primary care surveillance Hospital surveillance The former Yugoslav Republic of Macedonia Turkey ILI ARI SARI Laboratory-confirmed influenza Turkmenistan United Kingdom England Northern Ireland Scotland Wales Ukraine Uzbekistan 1 ILI data are reported but not included for the season to ensure consistent quality of data. 2 ILI/ARI data are available, but no denominator is reported. This weekly update was prepared by an editorial team at the European Centre for Disease Prevention and Control and the WHO Regional Office for Europe. The bulletin text was reviewed by the European Reference Laboratory Network for Human Influenza (ERLI-Net) coordination team: Adam Meijer, Rod Daniels, John McCauley and Maria Zambon. The bulletin text was reviewed by Isabelle Thomas (Scientific Institute of Public Health, Brussels, Belgium), Artan Simaku (Institute of Public Health, Albania) and Jens Nielsen (State Serum Institute, Copenhagen, Denmark). Maps and commentary do not represent a statement on the legal or border status of the countries and territories shown. All data are up-to-date on the day of publication. Past this date, however, published data should not be used for longitudinal comparisons as countries retrospectively update their databases. The WHO Regional Office for Europe is responsible for the accuracy of the Russian translation. Suggested citation European Centre for Disease Prevention and Control/WHO Regional Office for Europe. Flu News Europe, Joint ECDC WHO Regional Office for Europe Weekly Influenza Update, week 49/ Tables and figures should be referenced: European Centre for Disease Prevention and Control/WHO Regional Office for Europe. Flu News Europe, Joint ECDC WHO Regional Office for Europe Weekly Influenza Update, week 49/ World Health Organization European Centre for Disease Prevention and Control Reproduction is authorized, provided the source is acknowledged. 7