Saint Louis Encephalitis

Culex pipiens


Saint (St.) Louis Encephalitis virus (SLEV) is spread to people through the bite of infected mosquitoes. This virus is found in mosquitoes from Canada to Argentina although most human cases of disease have occurred in the United States. No cases have been reported from Connecticut. There is no vaccine to prevent or medicine to treat SLEV virus infection. The best way to prevent getting sick from SLEV is to prevent mosquito bites.


About St. Louis Encephalitis


Where in the United States Has SLEV Been Found?

ArboNET National Data


Information for Clinicians


Clinical Guidance


National Surveillance Case Definitions


Connecticut Provider Reporting Information 


Connecticut Laboratory Reporting Information



SLEV testing at the State Public Health Laboratory

State Public Health Laboratory Contacts – for additional information


Connecticut St. Louis Encephalitis Surveillance

In 2000, encephalitis was added to the state-wide reportable disease list, which included Saint Louis encephalitis (SLE). There have been no reported cases of SLE to the Connecticut Department of Public Health.

Connecticut Annual Infectious Diseases Statistics

Additional Resources

Connecticut Mosquito Management Program

Workplace Safety - Mosquito-Borne Diseases   NIOSH




This page last updated 11/4/2022.