Virus and ancient DNA: back to the future

Paleovirology, the study of ancient viruses, is a recent scientific development. It belongs to the domain of ancient DNA studies, paleogenetics. The analytical power of this discipline, that has many applications, is nevertheless limited by the poor conservation of DNA (and RNA) found in fossils and the subsequent methodological problems (amplification issues, post-mortem lesions, contaminations). These issues must be addressed in order to exploit the full potential of preserved nucleic acids within ancient remains. Once these difficulties have been overcome, it becomes possible to characterize ancient viruses and particular steps of their evolution or even adaptation to their hosts. Shedding light on key aspects of past epidemics allows for a better comprehension of present situations and for the anticipation of future situations where viral pathogens emerge or re-emerge. The examples described in this article illustrate these facts.