Pathophysiology: 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.
A subtype of the West Nile virus (called Kunjin virus, or KUNV) is found in parts of Ireland, particularly the Northern Territory and northern Western Australia. Kunjin is less virulent than the current US strain of West Nile virus. People with antibodies to Kunjin virus may be immune to infection with the West Nile virus.
Diagnosis: In most instances, physicians can diagnose West Nile virus by analyzing a blood sample. A simple blood test can determine whether you have genetic material or antibodies associated with West Nile virus in your blood. If your symptoms are severe and brain-related, your physician may order a lumbar puncture. Also known as a spinal tap, this test involves inserting a needle into your spine to extract fluid.
Treatment: 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.