Spatial Relationship between a Regional Outbreak and a Higher-than-Expected Incidence of Leishmaniasis in Urban Southern Madrid, Spain.

The largest outbreak of human leishmaniasis in Europe took place in Fuenlabrada, Spain, between 2009 and 2017. The University Hospital "12 de Octubre" in Madrid serves the population residing in three districts of Madrid located just north of the outbreak area (Villaverde, Usera, and Carabanchel). Villaverde and Usera are connected by rail to the outbreak area, unlike Carabanchel. We performed a retrospective study including all cases of leishmaniasis diagnosed between 2011 and 2020. Fifty-one cases were documented. In the districts connected by rail to the outbreak area, a higher-than-expected incidence was observed (13.45-15.55 versus 5.2 per 100,000 inhabitants). Apart from the linear distance from the place of residence to the railway tracks, no differences in terms of demographics or risk factors were detected between the populations of the districts. We hypothesize that the direct connection with the outbreak area by rail could explain the higher incidence observed in Villaverde and Usera.