Weekly influenza surveillance overview, 16 March 2012 - week 10

The reported national influenza trends indicate that the peaks of the epidemics have passed in a number of European countries, the latest edition of the Weekly Influenza Surveillance Overview highlights.

The 2011–2012 influenza season started late and has been without any clear geographic progression. During week 10/2012, medium or higher intensity has been reported in 20 countries, decreasing trends in ten countries and only three countries reported increasing trends.

Virological surveillance for the period shows that out of 1 433 sentinel specimens tested, 43.2% were positive for influenza virus, the second decline in a row this year. Of these sentinel viruses, 85.1% were type A and 14.9% were type B. This represents the highest percentage of B viruses so far, showing that the epidemics remain dominated by A(H3) viruses, but the proportion of B viruses are increasing late in the season.  Viral characterisation indicates an imperfect fit for the A(H3) component of the trivalent vaccine for this season with the circulating viruses.

Since week 40/2011, 1 238 SARI cases, including 51 fatalities, have been reported by seven countries. Of these cases, 873 were related to influenza infection – 97.4% with A viruses.

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