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Symptoms
By Mayo Clinic staff
Most have no 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:
- Skin rash
- Headache
- Fever
- Diarrhea
- Nausea
- Vomiting
- Backache
- Muscle aches
- Lack of appetite
- Swollen lymph glands
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 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
- Signs and symptoms similar to Parkinson's disease
- Lack of coordination
- Convulsions
- Pain
- Partial paralysis or sudden weakness
Symptoms of West Nile fever usually last three to six days, but symptoms of encephalitis or meningitis can linger for weeks, and certain neurological effects, such as muscle weakness, may be permanent.
