Recent advances in the molecular biology of west nile virus.

Since the mid-1990s, West Nile virus (WNV) has emerged as a significant agent of arboviral encephalitis in several regions of the world. In 1999, WNV was introduced into the northeastern United States and was associated with an outbreak of encephalitis affecting humans, birds and horses. Subsequently, the virus has spread across the country, and across southern Canada, and in 2002 and 2003 was associated with the largest outbreaks of arboviral encephalitis recorded in the Western hemisphere. Interestingly, the more recent spread of WNV into Mexico, Central America and the Caribbean has not been associated with the high levels of clinical disease observed in North America. This review addresses the most recent results from studies investigating the molecular biology and evolution of WNV, as well as progress in the development of diagnostic and therapeutic reagents.