Baseline levels of clinical influenza activity in Europe

Summary: Clinical influenza activity in Europe remains at baseline levels. Sporadic laboratory confirmed cases of influenza were detected in Latvia, Germany, Hungary, Portugal and Spain in week 47/2005. So far this season, 61% of total influenza virus detections (N=46) have been influenza A and 39% influenza B. No human cases of influenza A(H5N1) virus have been reported in Europe.

Epidemiological situation - week 47/2005: Twenty-four countries reported a low intensity of influenza activity in week 47/2005. Five countries (the Czech Republic, France, Lithuania, Slovakia and Poland) and one region (England Central) reported an increase in clinical activity compared to week 46/2005. However, the incidence of influenza-like illness or acute respiratory infections remained at baseline levels in all countries.

For the geographical spread of influenza, France and Latvia reported sporadic influenza activity, which means that isolated cases of laboratory confirmed influenza infection have been detected. All other countries reported no influenza activity, meaning that the overall level of clinical activity remained at baseline levels and influenza virus infections are not being laboratory confirmed.

Definitions for the epidemiological indicators can be found here.

Virological situation - week 47/2005: The total number of respiratory specimens collected by sentinel physicians in week 47/2005 was 331, of which two (0.6%) were positive for influenza A virus (one in Germany and one in Hungary). In addition, 904 non-sentinel specimens (e.g. specimens collected in hospitals) were analysed and five (0.6%) tested positive for influenza virus: one influenza A(H1) (Portugal) and four influenza B (Portugal (2), Latvia and Spain). Only one country reported a dominant subtype: influenza B in Spain.

Virological situation - 2005-2006 season (week 40-47/2005): Based on (sub)typing data of all influenza virus detections up to week 47/2005 (N=46; sentinel and non-sentinel data), 17 (37%) were influenza A (not subtyped), nine (20%) were A(H3) [of which five were A(H3N2)], two (4%) were A(H1) [of which one was A(H1N1)] and 18 (39%) were influenza B. Based on the characterisation data of all influenza virus detections up to week 47/2005, three have been antigenically and/or genetically characterized: two A(H3) A/Califormia/7/2004 (H3N2)-like and one A/New Caledonia/20/99 (H1N1)-like (click here). It should be noted that Scotland reported four genetic strain characterisations in week 46/2005: three A(H3) A/Califormia/7/2004 (H3N2)-like and one B/Shanghai/361/2002-like (click here).

Up to week 47/2005 no human cases of A(H5N1) influenza have been reported in Europe.

Comment: Clinical influenza activity in recent weeks has been low and all countries reported baseline levels of activity in week 47/2005. Sporadic laboratory confirmed cases of influenza have been detected across Europe so far this season. Among all influenza virus detections between week 40 and 47/2005 (N=46), 61% were influenza A and 39% influenza B. It is still too early to say which virus will be dominant in Europe during the 2005-2006 season

Whilst influenza activity in Europe remains low, a number of countries (England (click here [second graph]), France, Ireland, Latvia and Sweden) are reporting increases in laboratory detections of the respiratory syncytial virus (RSV), an infection with symptoms often similar to influenza.

Background: The Weekly Electronic Bulletin presents and comments influenza activity in 28 European countries. In week 47/2005, 24 countries reported clinical data and 26 countries reported virological data to EISS. The spread of influenza virus strains and their epidemiological impact in Europe is being carefully monitored by EISS in collaboration with the WHO Collaborating Centre in London, UK.

Other bulletins: To view national/regional bulletins in Europe and other bulletins from around the world, please click here. For a global update on the influenza A(H5N1) situation, please click here.