Primary Navigation for the CDC Website
CDC en EspaƱol

St. Louis Encephalitis

Image of Saint Louis Encephalitis as seen under a microscope

St. Louis encephalitis is one of the most common mosquito-transmitted human pathogens in the United States. St. Louis encephalitis virus is a flavivirus that was first identified in St. Louis, Missouri in 1933. St. Louis encephalitis is diagnosed based on symptoms, physical findings, laboratory testing, and the possibility of exposure to infected mosquitoes. There is no specific treatment for St. Louis encephalitis; care is based on symptoms. Steps to prevent infection with St. Louis encephalitis virus include use of insect repellent, protective clothing, and staying indoors while mosquitoes are most active. While periodic St. Louis encephalitis epidemics have occurred only in the Midwest and Southeast, St. Louis encephalitis virus is distributed throughout the lower 48 states (see map).

Information on St. Louis encephalitis virus can be found using additional Links and References.

Page last modified: October 11, 2007
Content Source:
Division of Vector Borne Infectious Diseases
National Center for Zoonotic, Vector-Borne, and Enteric Diseases