EISS Weekly Report: Week 46, 2004
Summary: While the intensity of influenza activity is still low in Europe and the incidence of clinical activity remains at baseline levels, six countries reported increasing clinical activity compared to the previous week. Latvia and Sweden reported their first cases of influenza B this season. The incidence of RSV detections is increasing in several countries, mainly on the western periphery of the area covered by EISS.
Epidemiological and virological situation: Twenty-one networks reported low intensity of influenza activity, meaning that there is no influenza activity or influenza activity is at baseline levels. However, six countries (Northern Ireland, England, Slovak Republic, Czech Republic, Poland and Latvia) reported increasing activity compared to the previous week.
Geographically, sporadic activity (i.e. isolated cases of laboratory confirmed influenza virus infection) was reported in five countries (England, France, Ireland, Latvia and Scotland). In the rest of Europe there was no activity.
The total number of respiratory specimens collected by sentinel physicians in week 46/2004 was 219, of which five (2.3%) were influenza virus positive. Of 644 non-sentinel specimens, five (0.8%) were positive. Of the ten positive specimens, eight were influenza A virus, five of which were not subtyped [from Ireland (3), Scotland (1) and France (1)] and three of which were subtyped A(H3) (England). The remaining two samples were influenza B virus (Sweden and Latvia).
Based on the (sub)typing data of all influenza virus detections up to week 46/2004 (N=37; sentinel and non-sentinel data), 13 were A (not subtyped), five were A(H1) [three of these were A(H1N1)], nine were A(H3) [five of these were A(H3N2)] and 10 were B.
Based on the characterisation data of all influenza virus detections up to week 46/2004 (N=37), seven have been antigenically and/or genetically characterised; four were A/Wellington/1/2004 (H3N2)-like (from England, France, Norway and Sweden), one was A/Fujian/411/2002 (H3N2)-like (from Germany) and two were A/New Caledonia/20/99 (H1N1)-like (from England and Ireland).
While the number of laboratory-confirmed cases of influenza shows only a slightly upward trend, the number of RSV cases clearly increased in six countries (Ireland, Scotland, Wales, England, France and the Netherlands).
Comment: Although the level of influenza activity in Europe remains low (at baseline levels) and there are only sporadic cases of laboratory confirmed influenza, there has been a slight increase in the number of positive cases of influenza. Apart from a single influenza B virus detection in Latvia, all nine influenza virus detections were in countries on the western periphery of the area covered by EISS (EISS area), similar to previous weeks. However, four of six countries signalling an increase in clinical influenza activity are located on the eastern periphery of the EISS area.
This week the proportion of influenza A viruses has increased with respect to B viruses (19 A to eight B). With the reporting of three more A(H3) viruses this week (England), the total number of A(H3) viruses is now nine, compared with five A(H1) viruses. It still remains too early to predict which of these influenza virus subtypes will dominate during the 2004-2005 season.
RSV activity started off and is on the rise in countries on the western periphery of the EISS area, similar to the observed influenza activity as measured by the detection of laboratory confirmed cases. Developments in RSV activity will be followed closely throughout the remainder of the season.
Background: The Weekly Electronic Bulletin presents and comments influenza activity in the 23 European countries (26 networks) that are members of the European Influenza Surveillance Scheme (EISS). In week 46/2004, 22 networks reported clinical data and 22 networks 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.
Other bulletins: To view national/regional bulletins in Europe and other bulletins from around the world, please click here.
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Map
The map presents the geographical spread of influenza and the intensity of activity as assessed by each of the networks in EISS.
Clicking on the map will, if available, take you though to the national web site. If ´regional´ activity is reported, a pop-up text box will appear which describes the activity in greater detail.
Clicking on England and France will provide you with regional data.
A = Dominant virus A
H1N1 = Dominant virus A(H1N1)
H3N2 = Dominant virus A(H3N2)
H1N2 = Dominant virus A(H1N2)
B = Dominant virus B
A & B = Dominant virus A & B
= : stable clinical activity
+ : increasing clinical activity
- : decreasing clinical activity
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Low = no influenza activity or influenza at baseline levels
Medium = usual levels of influenza activity
High = higher than usual levels of influenza activity
Very high = particularly severe levels of influenza activity
No activity = no evidence of influenza virus activity (clinical activity remains at baseline levels)
Sporadic = isolated cases of laboratory confirmed influenza infection
Local outbreak = increased influenza activity in local areas (e.g. a city) within a region,
or outbreaks in two or more institutions (e.g. schools) within a region. Laboratory confirmed.
Regional activity = influenza activity above baseline levels in one or more regions with
a population comprising less than 50% of the country´s total population. Laboratory confirmed.
Widespread = influenza activity above baseline levels in one or more regions with a population
comprising 50% or more of the country´s population. Laboratory confirmed.
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Network comments (where available)
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England
Influenza activity remains within baseline levels.
France
Sporadic flu detections/isolations and positive near patient tests in various regions in France. Activity indexes stay at baseline levels.
Latvia
Laboratory confirmation of the first influenza B virus in sentinel sample
Northern Ireland
The first RSV-A of the current season was detected in Week 46. All other detections since Week 40 have been RSV-B
Switzerland
No influenza virus detected last week.
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Table and graphs (where available)
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