Death from the Nile crosses the Atlantic: the West Nile Fever story.

The present paper reviews the American epidemic of West Nile Fever (WNF), which is the largest recorded outbreak ever. The epidemiological consequences of introducing a novel and immunologically unknown pathogen in a previously unexposed population and the possible evolution of a more pathogenic viral strain are discussed. In view of recent reports of imported cases in Denmark the issue of possible disease spread to Scandinavia is likewise addressed. However, the main scope of the article is to provide the clinician with an overview of the natural history, epidemiology and clinical characteristics of the disease.