Economic development leads to changing interactions between humans and their physical and biological environment. Worldwide patterns of human settlement in urban areas have led in developing countries to a rapid growth of mega-cities where facilities for housing, drinking-water and sanitation are inadequate, thus creating opportunities for the transmission of communicable diseases such as leishmaniasis. Increasing risk factors are making leishmaniasis a growing public health concern for many countries around the world. Certain risk factors are new, while others previously known are becoming more significant. While some risk factors are related to a specific eco-epidemiological entity, others affect all forms of leishmaniasis. Risk factors are reviewed here entity by entity.