The season of active circulation of influenza viruses has started in Europe, concludes Flu News Europe, the joint weekly influenza bulletin by ECDC and WHO/Europe, covering data up to 4 January 2015 (Week 1).
Influenza activity building up
While many countries in Europe still report low levels of influenza activity, the proportion of influenza-positive sentinel specimens has been above 10% for the third consecutive week. According to reports by EU/EEA countries, 26% of all sentinel specimens tested during week 1 were positive for influenza. In week 1, an increasing number of EU/EEA countries – Iceland, Malta, the Netherlands, Portugal, Sweden, UK – report medium intensity of influenza activity.
A(H3N2) viruses predominant so far
Influenza A(H3N2) viruses have been the predominant viruses detected across all surveillance systems. As indicated in ECDC’s recent Rapid Risk Assessment on circulation of drifted influenza A(H3N2) viruses in the EU/EEA, in previous seasons, influenza A(H3N2) viruses have been associated with more severe disease than A(H1N1) and type B viruses. Most of the A(H3N2) viruses characterized genetically belong to genetic subgroups containing viruses that have drifted antigenically compared to the A(H3N2) virus in use for the 2014–2015 northern hemisphere influenza vaccine. Such a drift usually signals reduced vaccine effectiveness against that particular strain.
Influenza vaccination protects the vulnerable
Influenza vaccination, which provides protection against at least three strains of influenza each season, remains the most effective measure to prevent illness and possibly fatal outcomes also this season, despite the drift in one of the influenza strains. In the EU, up to 40 000 people die prematurely during an average influenza season. Protecting those who are at risk of severe outcomes of influenza remains the priority of vaccination programmes, particularly the elderly and those vulnerable due to pre-existing illnesses or risk factors.
Antivirals should be considered
Treatment and post-exposure prophylaxis with antivirals protects the elderly and people in risk groups against serious influenza illness. The circulating viruses analysed so far show susceptibility to the antiviral drugs oseltamivir and zanamivir. As advised in previous seasons and in particular in a potentially severe season predominated by the A(H3N2) virus, physicians should always consider treatment or post-exposure prophylaxis with antivirals when treating influenza-infected patients and exposed individuals in risk groups.