Risk assessment: Seasonal influenza 2011–2012 in Europe (EU/EEA countries)

On 12 March 2012 ECDC published its annual risk assessment on seasonal influenza 2011/2012 in Europe. ECDC points out that on this occasion the seasonal influenza epidemics in Europe started unusually late and unlike the last few winters have not followed any particular geographical progression.

The annual EU season influenza risk assessment follows a structure that was established in the 2009 pandemic and gives an early description of the epidemics of seasonal influenza in the EU/EEA countries drawing on the experience of the first affected countries. The assessment identifies the special features of the current season, especially areas where public health or clinical actions are justified. It also highlights areas of uncertainty and therefore priorities for further work. The first ECDC seasonal influenza risk assessment was published in January 2011.

Virological surveillance data for the season shows that the epidemics have so far been dominated by the A(H3N2) viruses, but recently the proportion of B viruses has increased. The data also shows that some A(H1N1)pdm09 viruses are also circulating, although these are far lower in numbers than in the previous two seasons. However, they are over-represented among the people most severely affected that have been hospitalised with a confirmed infection. Antiviral resistance to the neuramindase inhibitors is almost non-existent this season.

At this stage, the role that B viruses will play towards the end of the season is uncertain. Other areas of uncertainty are the degree of effectiveness of the seasonal influenza vaccine in a season when there is an imperfect match between the vaccine and the circulating A(H3N2) viruses and the level of premature mortality that can be expected in older people due to the dominance of the virus A(H3N2). It will be difficult to tease apart the effects due to the influenza from those consequences of the cold weather.

ECDC annual seasonal influenza risk assessments

• The ECDC risk assessments are produced within an annual cycle which relates to the ECDC approach to severity of influenza. It is produced by a series of independent experts in the EU and draws on reports from national influenza representatives in the first affected countries in Europe. ECDC is grateful to the input from the experts and the representatives. Read more about the European approach to informing responses to the severity of influenza epidemics and pandemic  

• The ECDC annual risk assessments follows a WHO recommendation accepted by the World Health Assembly following the report from the independent report on the handling of the 2009 pandemic (the Fineberg Report)