Epidemiological features of parainfluenza virus infections: Laboratory surveillance in England and Wales, 1975-1997

Hospital laboratory reports of parainfluenza virus (PIV) infections from En gland and Wales between 1975 and 1997 were analysed with regard to PIV type and seasonality, and in addition, those between 1985-1997 with regard to a ge, sex and clinical features. Laboratory-based surveillance data highlight striking differences in the seasonality of different PIV types. PIV-3 repo rts demonstrated a clear annual epidemic cycle, with a peak usually occurri ng in late spring or summer, whereas peaks of PIV-1 and PIV-2 occurred at o ne or two year intervals, in the late autumn or early winter. PIV-4 also oc curred most frequently in the late autumn or early winter, but a clear epid emic cycle could not be identified. Laboratory surveillance data also provi de insight into the age and disease distribution of PIV infection in childr en and indicate severity of PIV infection in immunosuppressed adults. Of 82 21 PIV reports received between 1985-1997, PIV-3 accounted for 70.8, PIV-1 for 17.2, PIV-2 for 7.5, and PIV-4 for 1.1; 64.1 of reports came from infan ts under one year, 24.4 from children aged 1-4 years and 7.2 from individua ls aged 5 years or older, with an excess of males in all age groups. Bronch iolitis, croup and pneumonia occurred in association with all PIV types. In children under 1 year, PIV-2 infections were more likely to be associated with bronchiolitis than infections with other PIV types. In children under 15 years, croup was more frequently associated with PIV-1 and PIV-2 than wi th PIV-3 or PIV-4. In 392 (7.2) of the reported PIV infections between 1989 and 1997 an underlying condition was implicated, which included immunosupp ression or chronic cardiac or pulmonary disease. Considerable morbidity is associated with PIV infections in infants and young children and would make the widescale use of a vaccine a valuable public health intervention. Surv eillance information is essential to guide the development and use of preve ntive measures as well as to monitor their effectiveness.