Symptoms

Most people infected with the West Nile virus have no signs or symptoms.

Mild infection signs and symptoms

About 20% of people develop a mild infection called West Nile fever. Common signs and symptoms include:

• Fever
• Headache
• Body aches
• Vomiting
• Diarrhea
• Fatigue
• Skin rash

Serious infection signs and symptoms

In less than 1% of infected people, the virus causes a serious nervous system (neurological) infection. This may include inflammation of the brain (encephalitis) or of the membranes surrounding the brain and spinal cord (meningitis).

Signs and symptoms of neurological infections include:

• High fever
• Severe headache
• Stiff neck
• Disorientation or confusion
• Coma
• Tremors or muscle jerking
• Seizures
• Partial paralysis or muscle weakness
• Vision loss
• Numbness

Signs and symptoms of West Nile fever usually last a few days. But signs and symptoms of encephalitis or meningitis can linger for weeks or months. Certain neurological effects, such as muscle weakness, can be permanent.

When to see a doctor

Mild symptoms of West Nile fever usually resolve on their own. Seek medical attention right away if you have signs or symptoms of serious infection, such as severe headaches, a stiff neck, disorientation or confusion. A serious infection generally needs hospitalization.