Subclinical infection is common. Meningoencephalitis is the most common complication with cranial nerve palsies, motor weakness, abnormal reflexes and mental status changes. An outbreak in Romania in 1996 led to 400 neurologic cases, primarily in elderly patients. Uncomplicated illness cannot be differentiated from other non-specific febrile illnesses and dengue. West Nile Virus has not occurred in the Western Hemisphere until the recent New York City outbreak in October, 1999.
Treatment is supportive.