Mechanisms of viral emergence

Domingo, Esteban

It is not easy to specify at which stage of an emergence or re-emergence process virus variation plays a role and to what extent virus variation is essential or accessory. However, the presently available evidence suggests that viral genome variation participates in each of the processes that culminate in dissemination of the viral pathogen among individuals of the newly colonized host. Concerning the introduction step, current knowledge of viral population dynamics and of virus-host interactions suggests that chance encounters between viruses and potential new hosts must occur frequently. Consider the many areas of the world in which humans have regular contacts with animals or vectors that carry viruses (farm animals, mosquitoes, etc.) [89] . Most likely, only a tiny minority of such chance encounters gives rise to an emergence or re-emergence of a viral disease.