Weekly influenza surveillance in Europe for the 2012–2013 season started in week 40/2012. ECDC announced that the period of influenza transmission had started in week 49. In weeks 51 and 52, surveillance data in Europe are subject to particular delays and underreporting because of the holiday season so data should be interpreted with this in mind. In week 52, 20 of a potential 29 countries reported clinical data.
• During week 52/2012, four countries (France, Italy, the Netherlands and Norway) reported medium intensity transmission; geographic spread of influenza activity was reported as widespread by five countries (Belgium, Denmark, France, Norway and the UK (England)); and nine countries reported increasing trends.
• Of 375 specimens from sentinel patients, 25% were positive for influenza virus; a small decrease compared with 27% in the previous week. This may be related to a lower number of physician consultations over the New Year holiday.
• Since week 40/2012, 46% of sentinel specimens were type A and 54% were type B, though the proportion of B viruses has decreased somewhat in recent weeks. Subtying of type A viruses has shown proportions of 56% A(H3) and 44% A(H1).
• Viruses characterised to date match well with the vaccine viruses.
• Countries undertaking surveillance of laboratory-confirmed severe influenza cases requiring hospitalisation are starting to report increasing numbers of such individuals. 
Influenza activity continues to rise in a number of EU/EEA countries, especially in western Europe. Greater numbers of severe laboratory-confirmed cases are now being reported.