Ongoing influenza activity with a high intensity in parts of central and southern Europe
Key points: week 52/2009
Current situation: week 52/2009
- This report is based on data received from 39 of the 53 Member States in the WHO European Region.
- Thirty-three per cent of specimens collected from sentinel sources tested positive for influenza virus.
- The incidence of clinical respiratory illness has decreased over the past three weeks in 16 reporting countries.
- Influenza transmission remains high in some areas, particularly in the central and southern part of the Region.
- Out of 12 countries that reported testing at least 20 sentinel specimens for influenza this week, five reported that 30% of specimens or more had tested positive for influenza.
- Four countries reported high intensity of influenza activity, with six reporting moderate impact on health services.
- Pandemic (H1N1) 2009 was dominant in 27 countries and accounted 100% of influenza A virus subtype detections in sentinel specimens and 97% of detections in non-sentinel specimens.
- 2555 laboratory confirmed pandemic (H1N1) 2009 deaths have been reported in the Region.
Clinical respiratory disease activity has declined over the past three weeks in 16 countries. In many of these countries, the clinical consultation rate in the 5-14 year age group has again dropped below rates observed in the 0-4 year age group. However four of these 16 countries (Poland, Portugal, Switzerland and the United Kingdom) also tested at least 20 sentinel specimens for influenza during week 52/2009 and the median influenza positivity rate was 37% (mean 33%), suggesting that influenza circulation is ongoing despite declining clinical trends. The intensity of influenza transmission also remains high in some areas, particularly in the central and southern parts of the Region. Although the increase in clinical consultation rates reported during week 51/2009 in Georgia and Montenegro have not continued, 54% of sentinel specimens collected in Georgia tested positive for influenza during week 52/2009. In addition, Greece has reported that 73% of sentinel specimens tested positive for influenza, reflecting the highest positivity rate of any country testing 20 or more sentinel specimens this week. Although clinical consultation rates for ARI appear to have reached a second peak in Ukraine, clinical consultation rates remain high, particularly in central and eastern Ukraine. Georgia, Poland, the Russian Federation (Urals Region), Ukraine and Serbia reported the intensity of influenza circulation as high. Estonia, France, Georgia, Romania, Turkey and Ukraine reported the impact of influenza on health care services to be moderate.
Reports of respiratory hospitalizations and deaths to EuroFlu indicate that deaths due to acute respiratory infection (ARI) have continued to decline in the Russian Federation during each week since week 48/2009. The weekly count of hospitalizations due to severe acute respiratory illness (SARI) reported by Slovakia has also decreased from a peak that was observed in week 50. However, sentinel SARI hospitalizations reported by Ukraine again increased during week 52/2009, largely due to increases reported at sentinel sites in Kyiv and Odessa. Weekly reports of SARI hospitalizations in Uzbekistan have remained stable at a level similar to a peak that was reached in week 49/2009.
Virological update: week 52/2009
Sentinel physicians collected 942 respiratory specimens this week, of which 312 (33%) were positive for influenza virus. Of these virus detections, 312 (100%) were type A (300 pandemic A(H1), 12 not subtyped). Of the 13 countries testing 20 or more sentinel specimens this week, influenza-positive rates ranged from 0% (Hungary) to 72% (Greece), with a median of 36% and a mean of 34%.
Based on the antigenic characterization of 799 influenza viruses reported from week 40/2009 to week 52/2009, 792 were pandemic A(H1N1), A/California/7/2009-like, 3 were A/Perth/16/2009 (H3N2)-like, 2 were A(H3) A/Brisbane/10/2007 (H3N2)-like, 1 was A/Brisbane/59/2007 (H1N1)-like, and 1 was B/Brisbane/60/2008-like. Genetic characterizations were available for 252 isolates; all belonged to the A/California/7/2009 A(H1N1) pandemic influenza lineage.
Ten countries have tested isolates of pandemic (H1N1) 2009 virus for oseltamivir resistance. Of the 1312 cases tested, 26 were resistant to oseltamivir. All viruses tested for resistance to zanamivir (346/346) have been found to be zanamivir-sensitive and all viruses tested for resistance to adamantanes (64/64) have been found to be resistant. This week the Netherlands reported that one additional patient was retrospectively diagnosed with a monopopulation of H275Y oseltamivir resistant virus. This patient did not receive oseltamivir therapy and the epidemiological investigation is ongoing.
Sentinel surveillance systems throughout the Region suggest that influenza activity remains ongoing, and a high intensity of activity continues in parts of central and southern Europe. The percentage of sentinel specimens testing positive for influenza in the Region was 33% during week 52/2009. While this is lower than the peak of 45% that was reached during week 45/2009, this should be interpreted with caution as clinical consultation rates and the testing of sentinel specimens may be impacted by the holiday season.
The EuroFlu bulletin describes and comments on influenza activity in the 53 countries in the WHO European Region. Further information can be obtained from the WHO/Europe and WHO headquarters web sites.