Leptospirosis outbreak following the 2014 major flooding event in Kelantan, Malaysia- a spatial-temporal analysis.

Abstract

Introduction Severe floods have been shown to increase the risk of leptospirosis outbreaks in endemic areas. The purpose of this study is to determine the spatial-temporal distribution of leptospirosis in relation to environmental factors following a major flooding event in Kelantan, Malaysia. Methods We conducted a cross-sectional study of leptospirosis incident cases notified to the Malaysian Ministry of Health, from the 3 months pre, during, and 3 months post-flood periods, in reference to the severe 2014 Kelantan flooding event. Cases were analysed using the geographical information system to determine spatial distribution according to environmental parameters. Climatic factors influencing the incidence were also analysed. Results A total of 1229 leptospirosis cases were notified within the 3 study periods where incidence doubled in the post-flood period. A total of 19 out of 78 sub-districts recorded incidence rates of over 100 per 100,000 population during flood and in the post-flood periods, in comparison to only 4 sub-districts in the pre-flooding period. Average nearest neighborhood analysis indicated that cases were more clustered in the post-flood period as compared to the pre-flood period, with observed mean distance of 1138.8 meters and 1665.7 meters, respectively (both at p<0.01). Moran's I was higher in the post-flooding period (0.19; p<0.01) as compared to the pre-flood period (0.06; p<0.01). Geographic weighted regression showed that living in flooded areas close to rivers increased the risk of disease contraction. Kernel density also showed that post-flooding hotspots were concentrated near garbage cleanup areas. Leptospirosis incidence was also significantly associated with temperature, humidity, rainfall and river levels. Conclusion Leptospirosis outbreak after flooding was associated with several different factors. Understanding spatial distribution and associated factors can help improve future leptospirosis outbreak management following floods.