West nile virus (WNV) represents an important virus for American public health since its introduction to the northern hemisphere of this continent in 1999. This arbovirus produces a febrile illness and a neuroinvasive disease (encephalitis, meningitis or flaccid paralysis). Due to its epidemiological and virological features and the local presence of its reservoirs and vectors, WNV represents a serious menace and could become one of the next novel endemic diseases in Costa Rica. Therefore, it is important to be aware of the virological, clinical, epidemiological and diagnostic aspects regarding this virus in order to be prepared in case there is an increase in local incidence of WNV infection. In this review, the clinical, virological, epidemiological and diagnostic features associated to this virus are discussed.

West Nile Virus; pathogenesis; diagnostics; Costa Rica