St. Louis encephalitis virus (SLEV) is a spherical, single-stranded RNA virus with a diameter of 40 nm. It is a member of the Flaviviridae family. The vectors are mosquitoes in the Culex species: Cx. tarsalis and members of the Cx. pipiens complex in the western United States, Cx. pipiens and Cx. quinquefasciatus in the east, and Cx. nigripalpus in Florida.
Birds are the reservoir hosts of SLEV. Birds are not ill with the virus, but infect the mosquitoes who bite them. In urban and suburban areas, blue jays, robins, house sparrows, and pigeons are the main birds involved. People can be infected, as well as other domestic animals, but do not develop viremia; therefore, they are "dead-end" hosts.
45. CDC. Image #10228. This transmission electron microscopic (TEM) image revealed the presence of numerous St. Louis encephalitis (SLE) virions that were contained within a mosquito salivary gland tissue sample. PHIL public domain image. Created 1975. Accessed October 25, 2022. https://phil.cdc.gov/Details.aspx?pid=10228
