An Empirical Study on Human Leptospirosis Cases in the Western Province of Sri Lanka

Abstract

Leptospirosis is a zoonotic infectious disease in the world. It is growing as a major public health threat in Sri Lanka. The records in Sri Lanka show that, over 4000 cases were reported in the year 2016 in which nearly one fourth of total cases was reported only from the Western province. The objective of this study is to model leptospirosis cases in Western province of Sri Lanka using time series analysis. Since the purpose of forecasting is to plan the future activities, this study will support in term of planning the programmes of control for future. Appropriate tests were employed for the preliminary analysis to study the behavior of provinces-wise and district-wise distribution of leptospirosis cases in Sri Lanka. Seasonal Autoregressive Integrated Moving Average (SARIMA) models were developed using standard techniques. Diagnostic tests for tentatively fitted models were checked. In addition, for the purpose of selecting the best model, usual selection criteria were used. Finally, mean absolute percentage error was used to measure the accuracy of forecasting. The results show that, Western province (28.41%) is the mostly affected part of the island by human leptospirosis. Moreover, Gampaha (10.78%), Kalutara (9.59%) and Colombo (8.04%) districts in Western province are ranked among the first 5 districts of Sri Lanka based on average number of recorded cases. The accuracy of the fitted SARIMA(1, 0, 0)(0, 1, 1)12 model is over 85%. Therefore, it can be used to forecast future leptospirosis cases in the Western province. Based on the fitted model, the expected number of new cases in the Western province for the year 2017 is estimated to be 1168.