Abstract

In the season 1993/94 the virological NIVEL (Netherlands institute of primary health care)/RIVM-surveillance of respiratory virus infections was continued. The sentinel general physicians participating in the NIVEL network submitted 298 samples from patients with respiratory complaints From 92 (31%) of the samples a respiratory virus was grown, 67 of which were influenza A (H3N2) viruses. The antigenic reactivity of the strains in haemagglutination inhibition tests corresponded well with the virus isolates from diagnostic laboratories. When calculated per 10,000 persons, most influenza viruses were obtained from children aged 5-14 years. This is at variance with the NIVEL registration of influenza-like illnesses, which showed the highest incidence in the age group of 0-4 years. The protective effect of influenza vaccination over the seasons 1991/92, 1992/93, and 1993/94 was estimated at 76%.