Respiratory syncytial virus: a report of a 5-year study at a children's hospital.

A study over a 5-year period (1979-1983) of RSV infections in children in Sydney, Australia is reported. In common with findings made elsewhere in the world, annual epidemics of RSV infection commencing in autumn and lasting 4-6 months, with peak activity in mid-winter, were observed in 1979, 1980, and 1983. However, in 1981 and 1982 virus activity was first detected in midsummer, peaked in autumn, and was present throughout most months of the year. The alteration in virus activity in 1981 and 1982 was not associated with changes restricted to these 2 years in factors such as the age groups or sex ratio of patients affected or in the clinical categories predominantly affected. A study of climatic variables, however, indicated unusually low rainfall in 3 of 4 years encompassing this period. Study over a longer period is indicated to determine if these observed alterations in seasonal activity of RSV will be repeated in future years. Any possible relationship of such a change to rainfall could then also be better assessed.