Influenza activity increasing in western central Europe and decreasing in Spain: an update from EISS

Tamara Meerhoff (T.Meerhoff@nivel.nl)¹, Caroline Brown¹, Mary Cooke², Adam Meijer¹, John Paget¹, Maja Socan³, Jonathan Van Tam², Yves Thomas⁴, on behalf of EISS.

¹EISS co-ordination centre, NIVEL, Utrecht, the Netherlands;
²Health Protection Agency, London, United Kingdom;
³Institute of Public Health, Lubljana, Slovenia;
⁴H魀ital Cantonal Universitaire de Lyon de Gen鑦e, Geneva, Switzerland.

In week 4/2005 of the 2004-2005 influenza surveillance season, clinical influenza activity was at medium intensity in eight participating countries (Austria, England, France, Italy, Luxembourg, Portugal, Spain and Switzerland) and low in 16 other countries. Increasing clinical activity (compared with the previous week) was reported in 15 countries; the most notable rises occurring in Italy, Slovenia and Switzerland. Decreasing levels of influenza activity were reported by Ireland, England, Portugal and Spain.

Geographically, Belgium, France, Italy, Portugal, Spain and Switzerland reported widespread influenza activity and Austria reported regional activity. The Czech Republic, England, Germany, the Netherlands and Slovenia reported local activity and the other 12 networks reported sporadic or no activity.

The week 4 data indicate that influenza activity increased particularly in western central Europe. The high levels of influenza activity in Spain reported in previous weeks seem to have come to an end [1].

First results for week 5 in 2005 indicate a further increase in influenza activity in western central Europe (Switzerland, Slovenia, Austria, France, and Italy), which now also seems to be affecting the northern neighbouring countries of Belgium, Germany and the Netherlands. The initial decrease reported by Portugal in week 4, has reverted to an increase in influenza activity in week 5. Influenza activity in Europe is dominated by the A(H3) virus and most of these are A/Wellington/1/2004 (H3N2)-like viruses.

The total number of respiratory specimens collected by sentinel physicians was 1296: 23% tested positive for influenza virus. In addition, 213 non-sentinel specimens were influenza virus positive, bringing the total number of sentinel and non-sentinel positive specimens to 507. Of the 507 positive specimens, 468 were influenza A and 39 were influenza B. A total of 177 influenza A viruses were subtyped, 154 were A(H3) (of which 67 were A(H3N2)), 23 were A(H1) [of which 12 were A(H1N1) and three were A(H1N2).

Based on (sub)typing data of all influenza virus detections up to week 04/2005 of the 2004-2005 influenza surveillance season (n=3107; sentinel and non-sentinel data), 1671 (54%) were A (not subtyped), 1081 (35%) were A(H3) of which 331 were further subtyped as A(H3N2), 135 (4%) were A(H1) [68 further subtyped as A(H1N1) and three as A(H1N2)] and 220 (7%) were B. A total of 416 viruses (13% of all isolates) have been antigenically and/or genetically characterised: 258 A/Wellington/1/2004 (H3N2)-like viruses, 93 A/New Caledonia/20/99 (H1N1)-like viruses, seven A/Fujian/411/2002 (H3N2)-like viruses, two A/Panama/2007/99 (H3N2)-like viruses, 43 B/Jiangsu/10/2003-like viruses and 13 B/Hong Kong/330/2001-like viruses.

During the winter season (end of October to beginning of April) each year, the European Influenza Surveillance Scheme (EISS) monitors the spread of influenza virus strains and their epidemiological impact in Europe. It publishes a Weekly Electronic Bulletin which reports and comments on influenza activity in the 23 European EISS member countries (26 networks) (http://www.eiss.org) in collaboration with the World Health Organization Collaborating Centre for Reference and Research on Influenza in London.