St. Louis Encephalitis
St. Louis encephalitis is a mosquito-borne infection. This disease can affect the central nervous system, causing severe complications and even death.
The Central Nervous System
St. Louis encephalitis is caused by a virus. Mosquitoes are infected with this virus when they feed on birds. Infected mosquitoes can transmit the virus to humans and animals. St. Louis encephalitis is not spread from person to person.
Factors that may increase your chance of St. Louis encephalitis include:
- Increased age
- Living in or visiting the southern, central, or western United States, especially during the summer and fall
St. Louis encephalitis can result in a wide range of symptoms or produce no symptoms at all. The disease can be mild, severe, or even fatal.
Symptoms usually appear 5-15 days after the bite of an infected mosquito and may include:
Your doctor will ask about your symptoms and medical history. A physical exam will be done. Blood tests will also be done to identify the virus.
There is no specific treatment for St. Louis encephalitis. Treatment will focus on managing your symptoms and complications, such as through supporting breathing and providing fluids.
There is no vaccine against St. Louis encephalitis. Prevention of this disease centers on controlling mosquitoes and avoiding mosquito bites. Steps you can take to avoid mosquitoes include:
- Stay inside between dusk and dark. This is when mosquitoes are most active.
- Wear long pants and long-sleeved shirts when outside.
- Spray exposed skin with an insect repellent that contains up to 35% diethyltoluamide (DEET).
- Use proper mosquito netting at night. Look for netting treated with insecticide.
Centers for Disease Control and Prevention
National Institute of Allergy and Infectious Diseases
Public Health Agency of Canada
Reimann CA, Hayes EB, DiGuiseppi C, et al. Epidemiology of neuroinvasive arboviral disease in the United States, 1999-2007. Am J Trop Med Hyg. 2008;79(6):974-979.
Saint Louis encephalitis fact sheet. Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/sle. Updated June 11, 2007. Accessed January 4, 2013.
10/7/2013 DynaMed Plus Systematic Literature Surveillance http://www.dynamed.com/topics/dmp~AN~T208130/Encephalitis: Reimer LJ, Thomsen EK, Tisch DJ, et al. Insecticidal bed nets and filariasis transmission in Papua New Guinea. N Eng J Med. 2013;369(8):745-753.
Last reviewed November 2015 by David L. Horn, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.