Symptoms and Signs of West Nile Virus and West Nile Encephalitis (WNE)

Doctor's Notes on West Nile Virus and West Nile Encephalitis (WNE)

West Nile virus is a mosquito-borne viral illness. West Nile virus usually occurs in birds, and the virus is transferred from birds or animals to humans by the bite of an infected mosquito.

The majority of people infected with West Nile virus show no symptoms. When symptoms do occur, they can range from mild to a rapidly fatal brain infection. Early symptoms of West Nile virus infection include an abrupt onset of fever, chills, muscle aches, headache (may be severe), flu-like symptoms, sensitivity to light with pain behind the eyes, vomiting, diarrhea, rash, fatigue, and weakness. Most patients will recover completely. In a small percentage of patients, the disease can progress to cause encephalitis or meningitis, which may appear as neurological changes such as disorientation, tremors, seizures, headache, high fever, and neck stiffness, and in about 10% of cases, death.

Medical Author: John P. Cunha, DO, FACOEP
Medically Reviewed on 3/11/2019


Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.