Abstract :
New viral diseases seem to be emerging globally with increasing frequency. Most of the emergingviruses are zoonotic, that is, communicated by animals to humans. Many different factors cancontribute to the emergence of a new viral disease. These factors are: virological determinants,several genetic mechanisms that drive virus evolution such as mutation, recombination andreassortment; individual host determinants such as the host immune response, specific riskbehaviors and physiological factors; host population determinants such as human demographicsand behavior, international travel and community; environmental determinants such as ecologicaland zoonotic influences. These determinants need to be understood for prevention and controlof emerging viral diseases. Developments in molecular and genetic epidemiology are helpingus understand pathogen virulence, transmission patterns, and host susceptibility. Almost alwaysthere is a need for epidemiological field investigation to assess the risk to the human and/oranimal populations.
