Spatial distribution and cluster analysis of a leishmaniasis outbreak in the south-western Madrid region, Spain, September 2009 to April 2013

Since July 2009, there has been a community outbreak of leishmaniasis in south-west Madrid, Spain. The present study used the spatial distribution of cases to investigate the connection between the outbreak and a recently built peri-urban park. We included 157 cases of cutaneous (CL) and 90 cases of visceral (VL) leishmaniasis diagnosed at Fuenlabrada University Hospital between July 2009 and April 2013. CL and VL cases were geo-referenced and incidence rates by census tract were calculated. To identify high-risk areas, the spatial autocorrelation between individual cases was estimated. In a next step, areas where risk of disease was significantly increased were identified by cluster analysis. Higher incidence rates and the areas with highest intensity of CL and VL were located in the north-western part of the municipality. The most likely cluster of CL comprised three census tracks with relative risk (RR) = 11.5 (95% confidence interval (CI): 9.2-13.6). Two additional significant VL clusters were detected, the most likely one with RR = 9.2 (95% CI: 7.3-11.1). In addition, we found one significant VL cluster in the immigrant population (RR = 12.8; 95% CI: 9.3-16.1). The spatial pattern of leishmaniasis transmission revealed a relation between the outbreak and the suspected risk area.