Ecological and anthropological changes, as well as microbial evolution, are the essential driving forces behind the emergence or re-emergence of infectious diseases. Despite the extraordinary genetic versatility of bacteria and viruses, ecological and anthropological factors largely dominate asdrivers of the initial emergence episode. However, these episodes(spill-over) will only be consolidated by the existence of an expansion phase where opportunities for genetic alteration - and hence adaptation - of the pathogen are maximized, and their consequences more relevant and measurable in terms of their effect on epidemic dynamics. Two important points need to be borne in mind: genetic alterations that accentuate virulence and resistance can induce afitness cost that is incompatible with the long-term survival and transmissibility of the microbe in question. This is particularly true of resistance to certain antibiotics. The expansion phase also requires the intervention of ecological and anthropological factors (frequency of contact, travel, etc.).
Understanding the dynamics of emergence therefore requires the establishment of a solid "ecology-evolution" interface, the creation of a global research context bringing together microbiologists, evolutionary biologists, ecologists and anthropologists. The challenges are manifold:
- development of approaches integrating pathogen and host biology in epidemiological models of emergence, essential for the prevention and rapid control of epidemics;
- analysis of early epidemic phases and anticipation of their development;
- vaccine development;
- understanding the resistance mechanisms of microorganisms and their vectors;
- comparative genomic and phylogenetic analyses of pathogens, now essential for "tracing" intra/inter-species transmission routes and anticipating transmission efficiency;
- analysis of animal-vector infectious cycles (" one world-one health ") and study of host-pathogen interactions.
