[Emerging viral infections].

Emerging, re-emerging, rare or dangerous viruses are regularly citated in news. Most of theses viruses belong to the class 3 and 4. Clinical specimens must be handled with appropriate bio-security conditions, and, for some of them, high security facilities are required. In Geneva, a new P4D facility aiming to conduct diagnostic procedures targeting these viruses, fills a gap in Switzerland in this field. The goal of this review is to present some examples of past and ongoing viral outbreaks around the world, to present the virus classification according to the biological risk and to summarise basic knowledge concerning class 4 viruses.