Study of potential risk of dengue disease outbreak in Sri Lanka using GIS and statistical modelling

Objectives: The increasing incidence of dengue fever has become a priority health issue for Sri Lanka. Recent dengue outbreaks in Sri Lanka show two trends: yearly increase of total number of dengue incidence and increasing dengue outbreaks outside the endemic urbanised areas in the south and the west. Identification of factors responsible for dengue outbreaks and the mapping of potential risk areas in Sri Lanka are long overdue. This study examines the association between weekly rainfall patterns and dengue outbreaks in the western province between 2000 and 2004. Methods: The study develops a model to quantitatively assess the relationship between rainfall and dengue outbreaks and then evaluate the suitability of the model for predicting dengue outbreaks. A power regression model was constructed using rainfall and dengue incidence data. The Inverse Distance Weighted (IDW) interpolator and Geographic Information System (GIS) techniques were used in mapping the spatial distribution of dengue risk surfaces. Results: The results show that there is a strong correlation between dengue outbreaks and rainfall for majority of the towns studied. An error analysis was conducted to assess the validity of the model comparing model outputs and actual outbreaks. The analysis shows that the error component for selected cases is within a single outbreak. Conclusions: The ability to predict dengue outbreaks and mapping the spatial patterns facilitates dengue surveillance and monitoring.