[New viruses: myth, fantasy or reality?].

Emerging viruses previously unknown or partially known that infect repeatedly the human population are more than ever in the medias actuality headlines. Multiple factors may explain this dynamic. The most important is certainly the rapid evolution and the adaptation capacity of these viruses. Note that the increase in travel and international trade or climate change also play an important role. On the other hand, laboratory tests and current surveillance systems are more efficient. Thus, transmission of virus from an animal reservoir to human are more easily detected, accentuating the feeling of increasing phenomenon. Virological predictions have very low reliability in epidemiology. It is a reality that we have to accept.