Seasonal variations in the occurrence of urinary tract infections among children in an urban area in Finland.

The seasonal variations in the incidence of urinary tract infections (UTI) were studied in a series of 992 verified episodes of UTI treated between 1965 and 1974. The incidence was highest during November and lowest during the summer months. Summer episodes, moreover, tended to be the most severe. Seasonal variations were less marked among girls, than amond boys, except in the group of teenage girls in which peak incidences occurred in March and in September. Among the boys, a single peak incidence was recorded in July. The results of the analysis of weather type performed in this study showed that unseasonable types of weather, that is, cold and dry weather in autumn, warm and rainy weather in winter, and warm and dry weather in spring, were accompanied by a clear increase in the monthly number of episodes of UTIs. The difference in the monthly frequency of UTIs between the most and the least favourable types of weather was about two-fold.