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Symptoms
By Mayo Clinic staff
Most people infected with viral encephalitis have only mild, often flu-like symptoms, and the illness usually doesn't last long. In some cases, people might not have any symptoms. Possible symptoms include:
- Headache
- Irritability
- Lethargy
- Fever
- Joint pain
More serious infections can cause:
- Confusion and hallucinations
- Personality changes
- Double vision
- Seizures
- Muscle weakness
- Loss of sensation or paralysis in certain areas
- Tremors
- Rash
- Loss of consciousness
- Bulging in the soft spots (fontanels) of the skull in infants
When to see a doctor
See your doctor as soon as possible if you or your children experience signs and symptoms that suggest encephalitis, a disease that can be serious and life-threatening. Additionally, other potentially serious conditions can cause similar symptoms and also need to be considered.
Urgent signs and symptoms in children and adults may include:
- Altered levels of consciousness or hallucinations
- Muscle weakness or loss of feeling
- Seizures
- Mental disturbances
In infants, the key signs that immediate medical care is necessary are:
- Body stiffness
- Inconsolable crying
- Vomiting
- Bulging in the soft spots of the skull
- Encephalitis and meningitis fact sheet. National Institute of Neurological Disorders and Stroke. http://www.ninds.nih.gov/disorders/encephalitis_meningitis/detail_encephalitis_meningitis.htm. Accessed March 21, 2009.
- Tyler KL. West Nile virus infection in the United States. Archives of Neurology. 2004;61:1190.
- Johnson RP. Viral encephalitis in adults. http://www.uptodate.com/home/index.html. Accessed March 12, 2009.
- Willoughbly RE Jr, et al. Encephalitis, meningoencephalitis, acute disseminated encephalomyelitis, and acute necrotizing encephalopathy. In: Long SS, et al. Principles and Practice of Pediatric Infectious Diseases. 3rd ed. Philadelphia, Pa.: Churchill Livingstone; 2008. http://www.mdconsult.com/das/book/body/127224884-3/819357724/1679/50.html#4-u1.0-B978-0-443-06687-0..50049-7--cesec19_1078. Accessed March 21, 2009.
- Eastern equine encephalitis fact sheet. Centers for Disease Control and Prevention. http://www.cdc.gov/ncidod/dvbid/arbor/eeefact.htm. Accessed March 21, 2009.
- St. Louis encephalitis fact sheet. Centers for Disease Control and Prevention. http://www.cdc.gov/ncidod/dvbid/sle/Sle_FactSheet.html. Accessed March 21, 2009.
- LaCrosse encephalitis. Directors of Health Promotion and Education. http://www.dhpe.org/lacenceph.asp. Accessed March 21, 2009.
- Peters CJ. Infections caused by arthropod- and rodent-borne viruses. In: Fauci AS, et al. Harrison's Principles of Internal Medicine. 17th ed. New York, N.Y.: McGraw-Hill Medical; 2008. http://www.accessmedicine.com/content.aspx?aID=2895916. Accessed March 21, 2009.
- Encephalitis. The Merck Manuals: The Merck Manual for Healthcare Professionals. http://www.merck.com/mmpe/print/sec16/ch217/ch217c.html. Accessed March 21, 2009.
- Voelker R. Effects of West Nile virus may persist. Journal of the American Medical Association. 2008;299:2135.
- Insect repellant use and safety. Centers for Disease Control and Prevention. http://www.cdc.gov/ncidod/dvbid/westnile/qa/insect_repellent.htm. Accessed March 22, 2009.
- Follow safety precautions when using DEET on children. American Academy of Pediatrics. http://www.aap.org/family/wnv-jun03.htm. Accessed March 22, 2009.
