Abstract

At a crossroads between biology and medicine, epidemiology is the study of infectious and non infectious diseases in populations. In particular, epidemiology of infectious diseases relies on the articulation between the biology of the germ and the biology of the host population. Virus-host interactions are studied by epidemiologists at different levels and from different perspectives. The concept of emerging infectious disease, elaborated in the 1990s, emphasizes the need to investigate both the molecular and ecological aspects of virus-host interactions. Molecular approaches in epidemiology focus on the genetic, subcellular and cellular aspects of the host-germ relationship at the individual and population levels, while ecological approaches insist on the spatial distribution of host and germ populations, their relationships with their environment, and their interactions with other species. This paper describes integration processes at work between ecological and molecular approaches in the epidemiology of two RNA viruses since the advent of the concept of emerging infectious disease. Based on these two case studies, it further explores the meaning of integration, and aims at identifying the specific goals, challenges, expectations and issues associated with integration in these contexts.