Regular pattern of respiratory syncytial virus and rotavirus infections and relation to weather in Stockholm, 1984--1993.

OBJECTIVE: To seek the possible epidemiologic relationship between the two dominant pediatric infectious agents, respiratory syncytial virus (RSV) and rotavirus, and to analyze the relationship of RSV to influenza virus infections and climate. METHODS: In the laboratory register, we retrospectively identified pediatric cases less than 5 years of age from the period 1984--93 (including the winter of 1994). RSV was diagnosed by immunofluorescence in nasopharyngeal samples and rotavirus infections by electron microscopy of feces. RESULTS: We observed a regular and significant pattern of early RSV epidemics (December to February), alternating every other year with later ones (March to April). There were twice as many hospital admissions during early compared to late epidemics. There was a similar but reverse pattern of early and late rotavirus seasons. Influenza A virus outbreaks occurred during the same period as early RSV epidemics. Several weather factors, such as temperature, precipitation, wind force and humidity were analyzed in relation to RSV epidemics without disclosing an important relationship. Cloudiness was, however, found to be associated with RSV peaks. CONCLUSIONS: The possibility of predicting RSV epidemics may be useful for medical planning.