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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:
- Fever
- Headache
- Body aches
- Fatigue
- 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 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 weakness
Signs and symptoms of West Nile fever usually last a few days, but sign 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 or an altered mental state, seek medical attention right away. A serious West Nile virus infection generally requires hospitalization.
- West Nile virus: Clinical description. Centers for Disease Control and Prevention. http://www.cdc.gov/ncidod/dvbid/westnile/clinicians/clindesc.htm. Accessed May 19, 2010.
- West Nile virus: Epidemiologic information for clinicians. Centers for Disease Control and Prevention. http://www.cdc.gov/ncidod/dvbid/westnile/clinicians/epi.htm. Accessed May 19, 2010.
- West Nile virus: Fact sheet. Centers for Disease Control and Prevention. http://www.cdc.gov/ncidod/dvbid/westnile/resources/WNV_factsheet.pdf. Accessed May 19, 2010.
- Lindsey NP, et al. Surveillance for human West Nile virus disease - United States, 1999-2008. Morbidity and Mortality Weekly Report. 2010;59:1.
- Questions and answers: Symptoms of West Nile virus. Centers for Disease Control and Prevention. http://www.cdc.gov/ncidod/dvbid/westnile/qa/symptoms.htm. Accessed May 20, 2010.
- Petersen LR. Epidemiology and pathogenesis of West Nile virus infection. http://www.uptodate.com/home/index.html. Accessed May 26, 2010.
- Petersen LR. Clinical manifestations and diagnosis of West Nile virus infection. http://www.uptodate.com/home/index.html. Accessed May 26, 2010.
- Petersen LR. Treatment and prevention of West Nile virus infection. http://www.uptodate.com/home/index.html. Accessed May 26, 2010.
- Questions and answers: Prevention. Centers for Disease Control and Prevention. http://www.cdc.gov/ncidod/dvbid/westnile/qa/prevention.htm. Accessed May 20, 2010.
- What you need to know about mosquito repellent. Centers for Disease Control and Prevention. http://www.cdc.gov/ncidod/dvbid/westnile/mosquitorepellent.htm. Accessed May 19, 2010.
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