Molecular Epidemiology

Molecular epidemiology is now an established discipline in epidemiology.(1) It is the contemporary stage in the evolution of laboratory-based epidemiology that may have begun with the discovery in the late 1800s of ways to differentiate bacterial organisms by pure culture in artificial media.(2) Molecular epidemiology uses new molecular biology tools to address questions difficult or not possible to address by old laboratory tools. Just as statistical tools have become indispensable in epidemiological investigations and interpretations of epidemiologic data, molecular biology tools today have come to elucidate epidemiologic features of diseases that cannot be easily characterized by conventional techniques. Applied to infectious diseases, molecular biology methods have also come to challenge our traditional notions about the epidemiology of these diseases and have engendered novel opportunities for their prevention and control. This chapter will (1) review definitions commonly used in molecular epidemiology, (2) present an overview of molecular biology methods used to study infectious disease epidemiology, and (3) describe examples of the types of epidemiologic problems that can be addressed by molecular biology techniques, highlighting new concepts that emerged in the process of applying this approach to study bacterial infectious diseases.