Virus émergents ou menaces à répétition

Emergent viruses have attracted attention during years 2003 and 2004. Ancient fears have reappeared regarding pathogenic agents, capable to result in epidemics with high mortality rates. Such events constitute really repeated threats. The analysis of mechanisms permitting emergence of these viruses has shown that they are not random phenomenons, but they result from accumulated factors leading to transmission from animals to men. Several modes of transmission of infection include: either direct transmission, or by intermediate vectors (mosquitoes, ticks and other (mammals) animals). Convergence of ecologic, economic and epidemiologic factors confer to the epidemics potential ability do spread widely. With the development of surveillance networks and improvement in diagnostic technologies, these “new” viruses are better identified. Recent occurrence of SARS and of the avian influenza are best examples of such experiences.