St. Louis Encephalitis Virus

encephalitis stlouis
t. Louis Encephalitis (SLE) virus seen in a mosquito salivary gland Credit: Fred Murphy/Sylvia Whitfield Source: CDC

The St. Louis encephalitis virus is a member of the Flaviviridae subgroup and is related to Japanese encephalitis virus. This disease mainly affects the United States, but occasional cases have been reported in Mexico and Canada.

Most St. Louis encephalitis infections produce mild symptoms that include fever and headache. In more severe cases, high fever, neck stiffness, disorientation, tremors, coma, and convulsions can occur. Fatality rates range from 5%–30%, with the elderly more likely to suffer fatal infections.*

Vector insects

When Culex mosquitoes become infected with the St. Louis encephalitis virus by feeding on infected birds, they can transmit the virus to humans and animals during the feeding process. Only infected mosquitoes can transmit St. Louis encephalitis virus — once a human has been infected with the virus, it cannot be transmitted directly to other humans.

Links to vector distribution and habitats


Links to suggested vector-control solutions

Product selection dependent on vector biology and ecology

VectoLex FG
VectoMax FG


Culex quinquefasciatus Credit: Jim Gathany Source: CDC