| epidemiological features of parainfluenza virus infections: laboratory surveillance in england and wales, 1975-1997. | hospital laboratory reports of parainfluenza virus (piv) infections from england 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 age, sex and clinical features. laboratory-based surveillance data highlight striking differences in the seasonality of different piv types. piv-3 reports demonstrated a clear annual epidemic cycle, with a peak usually occurring in late spring or summer, whereas peaks of piv- ... | 1999 | 10442474 |