Seasonal variations in admissions to a tropical paediatric unit

The monthly admissions over the last 10 years (1972-1981) of children with common illnesses to the Department of Paediatrics, National University of Singapore, were analyzed to ascertain if there were any significant seasonal patterns. The method used (developed by Walter and Elwood) consists of estimating the amplitude of seasonal variations and the time at which the maximum occurs in a postulated simple harmonic fluctuation. Six out of the 9 diagnostic groups studied were found to have significant seasonal variations in at least 5 out of 10 years or 3 out of the last 5 years: pharyngitis, bronchitis, broncho-pneumonia, bronchial asthma, gastro-enteritis, and febrile convulsions. Febrile convulsions showed the best correlation (in terms of the number of monthly admissions) with the other illnesses showing seasonal fluctuations. Admissions for bronchial asthma were negatively correlated with the others. No consistent pattern in the time of peak number of admissions was discernable. The seasonal variations demonstrated are probably related to outbreaks of viral infections which tend to occur round the year in the tropics.