While having public health and prevention campaigns as its main aims, epidemiology is also engaged in the elaboration of causal explanations of more or less common diseases. Long neglected by the philosophy of science, epidemiology is currently manifesting a strong interest in foundational and methodological issues. I shall here refer to a wide debate underway in the last decade involving the definition, status and methods of the epidemiology discipline, and relating what it is to explain a disease in epidemiological terms as a complex and multilevel phenomenon. I shall consider how such reflections can relate to some recent philosophical works on causal explanation, and how issues emerging from epidemiology can challenge them.