[Influenza in the 1996/'97 season; vaccine composition for the 1997/'98 season].

The first indication of flu activity in the Netherlands in the 1996/'97 season was the isolation of an A/H3N2 influenza virus in week 48 of 1996. In subsequent weeks influenza viruses were isolated sporadically. The clinical influenza activity increased from week I of 1997 and reached its peak in week 4 of 1997. Simultaneously with the increase of clinical influenza activity, an increasing number of influenza viruses were isolated. The epidemic had a relatively small extent. Initially, A/H3N2 influenza viruses were predominant, but in the second half of the epidemic an increasing number of influenza B viruses were isolated as well. The A/H3N2 viruses were antigenically fairly strongly distinct from the variants prevalent in the preceding years. This season influenza A/HINI viruses did not play a significant role and only one virus of this subtype was isolated. All influenza A/H3N2, A/HINI and B viruses isolated were antigenically similar to the vaccine strains.