West Nile virus (WNV) is a neurotropic flavivirus that has emerged globally as a significant cause of viral encephalitis. Infection of humans is associated with a febrile illness that can progress to a lethal encephalitis with symptoms including cognitive dysfunction and flaccid paralysis. Seroprevalence studies suggest that while the majority of WNV infections are asymptomatic, approximately 20 to 30% of infected individuals develop flu-like clinical manifestations characterized as WNV fever.
On 6th October, 2003 a case of human West Nile virus (WNV) infection was notified by the Centre National de référence des Arbovirus. Twenty patients who had been hospitalized at some time from August 1 to October 15, 2003, for febrile meningitis, encephalitis, or polyradiculoneuritis were screened. Four patients in whom cerebrospinal fluid (CSF) analysis indicated a viral cause were included.
The diagnosis of West Nile virus infection is confirmed with a blood or cerebrospinal fluid test. There is no specific treatment for West Nile virus infection. Intensive supportive therapy is directed toward the complications of brain infections. Anti-inflammatory medications, intravenous fluids, and intensive medical monitoring may be required in severe cases.
The Department for Environment, Food & Rural Affairs (Defra) said in a preliminary outbreak assessment published [in September 2015], that the cases of the mosquito-borne disease occurred in the Bouches du Rhone region, in the south of France. In 1 of the first cases, a 3-year-old Lusitano horse showed neurological signs and was euthanised. In another, an Anglo-Arabian mare also showed clinical signs and was similarly put down. Both occurred in August 2015.