West Nile Fever: An Overview

West Nile fever is a mosquito-borne illness caused by the West Nile virus (WNV), a member of the Flavivirus genus. First identified in Uganda in 1937, WNV has since spread globally, with significant outbreaks reported in Africa, Europe, Asia, and North America. The virus is primarily transmitted by Culex mosquitoes, which acquire the virus from infected birds, the main reservoir hosts. Humans and other mammals are incidental hosts, typically contracting the virus through mosquito bites. Other less common transmission routes include blood transfusions, organ transplants, and from mother to baby. Epidemiologically, West Nile fever exhibits seasonal peaks in late summer and early fall. Risk factors for infection include advanced age, immunocompromised states, and outdoor activities that increase mosquito exposure. Clinically, approximately 80% of infected individuals are asymptomatic. Symptomatic cases often present with fever, headache, fatigue, and a maculopapular rash. Severe neuroinvasive disease, occurring in less than 1% of cases, can manifest as encephalitis, meningitis, or acute flaccid paralysis, predominantly affecting the elderly and immunocompromised. Gross pathology in severe cases may show inflammation in the brain and spinal cord. Histopathological findings typically include perivascular lymphocytic infiltration, microglial nodules, and neuronal degeneration. Diagnosis is primarily based on clinical presentation and confirmed through laboratory tests such as serum or cerebrospinal fluid (CSF) IgM antibody capture enzyme-linked immunosorbent assay (MAC-ELISA), reverse transcription-polymerase chain reaction (RT-PCR), and viral culture. Prevention of West Nile fever focuses on vector control and personal protective measures. Strategies include eliminating standing water to reduce mosquito breeding sites, using insect repellents containing DEET, and wearing protective clothing. Public health efforts also involve surveillance of mosquito populations and monitoring virus activity in birds and humans. Currently, there are no specific antiviral treatments or vaccines available for West Nile fever, with management being supportive and symptom-focused. Research continues to develop effective vaccines and therapeutic options to combat this emerging infectious disease.