Résumé
Molecular epidemiology designates the various molecular methods that aim to identify the relevant units of analysis of pathogens involved in transmissible diseases: species, subspecies, strains, clones and genes of interest. It is frequently based on an empirical approach. I advocate that evolutionary concepts enrich this discipline considerably and should be considered as an integral part. In turn, the experience and questioning of field experts are crucial to evolutionists who use transmissible diseases as models. A molecular epidemiology aim gives evolutionary studies a practical goal, putting a stop to approaches that are overly speculative.