Eurosurveillance - Volume 7, Issue 11, 01 November 2002

Influenza activity in Europe during the 2001-02 influenza season was mild to moderate. Compared to historical data, the intensity was low in six countries, medium in eleven and high in one country (Spain). The dominant virus circulating in Europe was influenza A(H3N2). Two novel influenza virus strains were isolated during the 2001-02 season: influenza A(H1N2) viruses (mainly isolated in the United Kingdom and Ireland, but also in Belgium, France, Germany, the Netherlands, Portugal, Sweden, Switzerland and Romania), and influenza B viruses belonging to the B/Victoria/2/87 lineage (mainly isolated in Germany, but also sporadically in France, Italy, the Netherlands and Norway). With the exception of H1N2 virus detections in England, and Ireland and the influenza B viruses belonging to the B/Victoria/2/87 lineage in Germany, these two viruses did not circulate widely in Europe and did not play an important role in influenza activity during the 2001-02 season. An influenza B virus belonging to the B/Victoria/2/87 lineage will be included in the 2002-03 influenza vaccine. The new subtype influenza A(H1N2) is covered by the 2002-03 vaccine, as the haemagglutinin and neuraminidase components of the H1N2 viruses are antigenically similar to the vaccine components (H1N1 and H3N2).

EISS implemented an evaluation protocol to assess the quality of clinical data collected by sentinel networks for the surveillance of influenza. The protocol was applied in Belgium and in three regions in Spain where it resulted in recommendations to improve the national and regional surveillance networks.

The Quality Control Assessment (QCA) was initiated to evaluate the quality of the influenza and respiratory syncytial virus (RSV) testing in the national reference centres belonging to the European Influenza Surveillance Scheme (EISS) network. Samples were coded and sent in two panels of 12 samples within a two week interval to 16 laboratories during the 2000-01 winter season. The antibodies titration by HI test was reported by 60% of the laboratories (n=16), and the results were correct for 56% of them. One false detection of influenza B antibodies was reported by one laboratory, and for the others the sensitivity varied widely. The sensitivity of the tests for the detection of influenza virus varied for A(H3N2) from 10 to 100 000 TCID50/ml. The influenza A subtyping was performed by 87% of the laboratories, and 31% gave correct results. The characterisation of the variants was undertaken by six laboratories and half of them fully achieved it. Fifty six percent of the laboratories used RT-PCR for the diagnosis; the results were specific and the sensitivity equivalent to the cell culture.

In November 2001 the European Commission invited experts from all over Europe to express their views on ways to improve preparedness for an influenza pandemic at the European Community level. The conference was well attended and key actions to be addressed by public health authorities in cooperation with decision makers and the pharmaceutical industry were identified (1).