Respiratory virus isolates made at the National Institute for Virology from 1982 to 1991 were studied. An active virus surveillance programme, 'viral watch', which recruits throat swab specimens from a network of monitoring centres--mainly in the Witwatersrand and Vereeniging area with one centre in Middelburg--that represent a cross-section of the population, provided 68% of the specimens and 74% of the isolates, with an isolation rate of 25.5%. This was significantly higher than that of

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... e specimens (17.7%). Of the 966 isolates, influenza viruses accounted for 527 (54.7%), para-influenza for 122 (12.6%), respiratory syncytial virus for 34 (3.4%) and adenovirus for 106 (11.0%). Influenza viruses showed a definite seasonal peak between June and August whereas the other viruses, although they showed a winter predominance, were isolated throughout the year. An active virus surveillance programme is particularly valuable in monitoring respiratory virus epidemiology in the population.