English Abstract In the season 1992/93 the clinical influenza
surveillance among general practioners participating in the NIVEL
(Netherlands institute of primary health care) system was supplemented by
RIVM with virological laboratory examinations. Respiratory samples were
taken from 388 patients with respiratory symptoms suggestive of influenza.
From 127 specimens (33%) a virus was isolated, which was influenza virus
(mainly type B) in 87 cases. Compared with virological surveillance based
on virus isolations from hospital admitted patients this new influenza
surveillance system proved a better early warning system. The first
influenza B virus strain of the season 1992/93 isolated in the Netherlands
was isolated in this system about six weeks before the start of the
epidemic. It was also more efficient: it yielded 43% of all influenza virus
strains of the season 1992/93 isolated in the Netherlands. The period
showing many clinical cases of influenza-like illness coincided with that in
which many influenza viruses were isolated.