Emerging infections of the central nervous system.

Emerging infections affecting the central nervous system often present as encephalitis and can cause substantial morbidity and mortality. Diagnosis requires not only careful history taking, but also the application of newly developed diagnostic tests. These diseases frequently occur in outbreaks stemming from viruses that have mutated from an animal host and gained the ability to infect humans. With globalization, this can translate to the rapid emergence of infectious clusters or the establishment of endemicity in previously naïve locations. Since these infections are often vector borne and effective treatments are almost uniformly lacking, prevention is at least as important as prompt diagnosis and institution of supportive care. In this review, we focus on some of the recent literature addressing emerging and resurging viral encephalitides in the United States and around the world-specifically, West Nile virus, dengue, polio, and cycloviruses. We also discuss new, or "emerging," techniques for the precise and rapid diagnosis of encephalitides.