A viral encephalitis caused by the St. Louis encephalitis virus (encephalitis virus, st. louis), a flavivirus. It is transmitted to humans and other vertebrates primarily by mosquitoes of the genus culex. The primary animal vectors are wild birds and the disorder is endemic to the midwestern and southeastern United States. Infections may be limited to an influenza-like illness or present as an aseptic meningitis or encephalitis. Clinical manifestations of the encephalitic presentation may include seizures, lethargy, myoclonus, focal neurologic signs, coma, and death. (From Adams et al., Principles of Neurology, 6th ed, p750). The disease is Monarch Disease Ontology entry MONDO_0005969 (st. Louis encephalitis). Also known as: Neuroinvasive St. Louis encephalitis virus infection, Saint Louis encephalitis, St. Louis encephalitis virus caused infectious encephalitis, St. Louis encephalitis virus infectious encephalitis.