West Nile Virus Infection: Virology, Epidemiology, Pathogenesis, Clinical Manifestations, and Public Health Implications

West Nile Virus (WNV) is a single-stranded, positive-sense RNA virus of the genus Flavivirus, family Flaviviridae. It is a mosquito-borne arbovirus maintained in an enzootic cycle primarily between Culex species mosquitoes and avian hosts. Humans and equids are incidental, dead-end hosts. Since its emergence in New York City in 1999, WNV has become endemic throughout the Americas, Europe, Africa, Asia, and Australia, posing a significant global public health threat. The majority of human infections are asymptomatic; however, approximately 20% result in West Nile Fever, a self-limiting febrile illness. In less than 1% of cases, the virus invades the central nervous system, causing severe neuroinvasive diseases such as meningitis, encephalitis, and acute flaccid paralysis, with potential for long-term neurological sequelae and death, particularly in the elderly and immunocompromised. This review provides a comprehensive overview of the WNV, detailing its classification, structure, and genomic organization. It elaborates on the viral replication cycle within the host cell, from receptor-mediated endocytosis to assembly and release. The epidemiology and transmission dynamics, including the role of migratory birds in global dispersal, are examined. The pathogenesis of WNV, from initial cutaneous infection to neuroinvasion, is described alongside the clinical spectrum of disease. Current diagnostic methods, primarily serological detection of IgM antibodies, are discussed, along with the supportive nature of available treatments and the emphasis on public health prevention strategies. The review concludes that WNV remains a persistent and re-emerging pathogen, necessitating continued surveillance, vector control efforts, and research into effective antiviral therapies and vaccines.