West Nile fever is a viral zoonosis that primarily affects the central nervous system. It is transmitted to humans and animals through the bite of infected mosquitoes, which are themselves reservoirs for the virus. The causative agent belongs to the flavivirus genus and is maintained in enzootic cycles, typically between avian populations and mosquito vectors. Symptoms can range from asymptomatic infection to mild illness characterized by fever and headache. In severe cases, the infection can lead to neuroinvasive manifestations, resulting in encephalitis or meningitis. Prevention efforts focus on vector control measures to reduce mosquito populations and limit human exposure to the biting vectors.