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Symptoms
By Mayo Clinic staff
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.
- West Nile virus: Questions and answers. Centers for Disease Control and Prevention. http://www.cdc.gov/ncidod/dvbid/westnile/qa/symptoms.htm. Accessed Sept. 5, 2012.
- West Nile virus: Fact sheet. Centers for Disease Control and Prevention. http://www.cdc.gov/ncidod/dvbid/westnile/wnv_factSheet.htm. Accessed Sept. 5, 2012.
- Petersen LR. Clinical manifestations and diagnosis of West Nile virus infection. http://www.uptodate.com/ index. Accessed Sept. 5, 2012.
- Ferri FF. Ferri's Clinical Advisor 2013: 5 Books in 1. Philadelphia, Pa.: Mosby Elsevier; 2012. http://www.mdconsult.com/books/about.do?eid=4-u1.0-B978-0-323-08373-7..00002-9&isbn=978-0-323-08373-7&about=true&uniqId=343863096-23. Accessed Sept. 6, 2012.
- West Nile virus. National Institute of Allergy and Infectious Diseases. http://www.niaid.nih.gov/topics/westnile/understanding/pages/what.aspx. Sept. 6, 2012.
- Centers for Disease Control and Prevention, et al. West Nile virus and other arborviral diseases — United States, 2011. MMWR. 2012;61:510. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6127a3.htm?s_cid=mm6127a3_w. Accessed Sept. 5, 2012.
- Petersen LR. Treatment and prevention of West Nile virus infection. http://www.uptodate.com/ index. Accessed Sept. 5, 2012.
- Updated information regarding insect repellants. Centers for Disease Control and Prevention. http://www.cdc.gov/ncidod/dvbid/westnile/RepellentUpdates.htm. Accessed Sept. 7, 2012.
- Anderson CF (expert opinion). Mayo Clinic, Rochester, Minn. Sept. 10, 2012.
- Mahoney KR (expert opinion). Food and Drug Administration, Rockville, Md. Jan. 10, 2011.
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