During week 51/2012, two of 17 countries reporting clinical data experienced medium intensity influenza activity, three countries reported geographically widespread influenza activity, and five additional countries reported increasing trends.

The proportion of sentinel specimens positive for influenza continued to increase (27.3%), compared with 17.3% in week 50. Seventy per cent of influenza viruses were type A and 30% were type B. So far the detected viruses remain well-matched to the vaccine strain.

Since week 40/2012, 10 hospitalised severe influenza cases have been reported by five countries. Sixty per cent of these infections were due to influenza A viruses.