ABSTRACT
Emerging viruses are classified as those viruses that are new to human hosts, rising significantly in incidence, or have established endemicity in a new geographic location. New, emerging, and re-emerging viruses are a perpetual threat to human health. Many viruses are biologically primed to evolve more rapidly than their hosts, and viruses that emerge in new hosts often undergo a period of rapid diversification as they adapt to their new habitat. Many emerging and re-emerging human-pathogenic viruses cause acute febrile disease processes that exhibit overlapping clinical signs and symptoms. Outbreaks stemming from emerging viruses often evoke emergency response protocols based on prior observations of transmission dynamics, incubation period, and persistence of pathogen shedding. The emergence of novel viral pathogens, previously unreported pathologies associated with known viral agents, and the re-emergence of previously well-controlled viruses, is a constant factor in human health.
