St. Louis Encephalitis
by Krisha McCoy, MS
St. Louis encephalitis is a mosquito-borne infection. This disease can affect the central nervous system, causing severe complications and even death.
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 chances of St. Louis encephalitis:
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:
Centers for Disease Control and Prevention
National Institute of Allergy and Infectious Diseases
Mosquito avoidance. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T115142/Mosquito-avoidance . Updated November 21, 2016. Accessed December 7, 2017.
Saint Louis encephalitis fact sheet. Centers for Disease Control and Prevention website. Available at:
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Updated June 11, 2007. Accessed December 7, 2017.
Last reviewed November 2018 by EBSCO Medical Review Board David L. Horn, MD, FACP
Last Updated: 12/20/2014
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