Weekly influenza surveillance overview March 30 2012 - Week 12

Surveillance report

The weekly influenza surveillance overview is a collection of timely and relevant information regarding influenza activity in Europe. It provides key statistical data on a vareity of issues including the following: sentinel surveillance of influenza-like illness (ILI) and acute respiratory illness (ARI), virological surveillance, hospital surveillance of severe acute respiratory infection (SARI), mortality surveillance and qualitative reporting. An up-to-date report is available on Fridays.

Executive summary

The 2011–2012 influenza season started late and has been without any clear geographic progression. During week 12/2012, medium or low intensity was reported in all 28 reporting countries, with decreasing trends in 21 countries. Of those, 14 countries reported decreasing trends for two consecutive weeks, suggesting that their influenza seasons have peaked.

Virological surveillance for the period shows that of 940 sentinel specimens tested, 42.9% were positive for influenza virus. This proportion was unchanged compared to week 11 after declining steadily from a peak of 58% in week 8. Of the positive sentinel specimens, 75.2% were type A and 24.8% type B. The proportion of influenza B viruses has continued to increase.

Since week 40/2011, a total of 1 513 SARI cases, including 79 fatalities, have been reported by seven countries. Of these cases, most were influenza-related.

No resistance to neuraminidase inhibitors (oseltamivir and zanamivir) has been reported so far this season.