Most have no signs or symptoms

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

Mild infection signs and symptoms

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

  • Fever
  • Headache
  • Body aches
  • Fatigue
  • Back pain
  • Skin rash (occasionally)
  • Swollen lymph glands (occasionally)
  • Eye pain (occasionally)

Serious infection signs and symptoms

In less than 1 percent of infected people, the virus causes a serious neurological infection. Such infection may include inflammation of the brain (encephalitis) or of both the brain and surrounding membranes (meningoencephalitis). Serious infection may also include infection and inflammation of the membranes surrounding the brain and spinal cord (meningitis), inflammation of the spinal cord (West Nile poliomyelitis) and acute flaccid paralysis — a sudden weakness in your arms, legs or breathing muscles. Signs and symptoms of these diseases include:

  • High fever
  • Severe headache
  • Stiff neck
  • Disorientation or confusion
  • Stupor or coma
  • Tremors or muscle jerking
  • Lack of coordination
  • Convulsions
  • Pain
  • Partial paralysis or sudden muscle weakness

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

When to see a doctor

Mild symptoms of West Nile fever usually resolve on their own. If you experience signs or symptoms of serious infection, such as severe headaches, a stiff neck, disorientation or confusion, seek medical attention right away. A serious West Nile virus infection generally requires hospitalization.

Dec. 18, 2012