Spatial and seasonal analysis of human leptospirosis in the District of Gampaha, Sri Lanka

Leptospirosis is a zoonostic infectious disease, caused by a pathogenic species of the Genus Leptospira. In recent years, a markedly increased number of leptospirosis cases have been reported in the District of Gampaha, in the Western Province of Sri Lanka. Typically, the risk of the disease in the district is seasonal with a small spike occurs in March to May and a large spike occurs during October to December. Objectives of this study were to analyze spatial and seasonal patterns of human leptospirosis and to predict the leptospirosis epidemic trend in the District of Gampaha, Sri Lanka. All Divisional Secretariats (DS) of the district of Gampaha were selected for the study. Epidemiological data were obtained from the Regional Epidemiological Unit, Gampaha. The leptospirosis cases were georeferenced according to DS in where these cases were reported. The cumulative incidence and the fatality were calculated for each DS. Of the georeferenced data, highest mean (±S.E.) of number of leptospirosis cases (72.60 ±15.54) were observed from DS of Mirigama. The highest mean cumulative incidence (4.97±1.10) and case fatality rate (3.88±2.42) were observed from DS of Divulapitiya and Katana respectively. According to past 10 years data on leptospirosis, highest mean numbers of leptospirosis cases were reported in March (51.00±12.99) and November (56.80±8.27). A predictive model for clinically confirmed human leptospirosis was designed for the district by using TSA package of the statistical software R. This study provides an evidence base for reducing disease burden by improving the understanding of the dynamic patterns of the disease in the District of Gampaha, Sri Lanka.