La Crosse Encephalitis

Definition

A mosquito-borne viral disease caused by La Crosse virus (genus Orthobunyavirus, family Peribunyaviridae), characterized by inflammation of the brain and primarily affecting children in endemic regions of the United States. The disease exemplifies the public health significance of container-breeding mosquitoes and forest-edge habitats in zoonotic disease transmission cycles.

Etymology

Named for La Crosse, Wisconsin, where the virus was first isolated in 1964 from a fatal pediatric case.

Example

In the Appalachian and upper Midwestern United States, La Crosse encephalitis cases peak in late summer when Ochlerotatus triseriatus (the eastern treehole mosquito) populations surge in suburban areas with discarded tires and water-holding tree cavities.

Synonyms

• LACV encephalitis
• California serogroup encephalitis (informal subset)

Related Terms

• Arbovirus
• vector-borne disease
• Ochlerotatus triseriatus
• viral encephalitis
• Zoonosis
• mosquito-borne disease
• orthobunyavirus
• enzootic cycle

Usage Notes

Distinguished from other California serogroup viruses (e.g., California encephalitis virus, Jamestown Canyon virus) by its specific vector association and geographic concentration. The term refers specifically to the clinical disease; 'La Crosse virus' or 'LACV' denotes the causative agent. Not all infections result in encephalitis—most are asymptomatic or present as nonspecific febrile illness. Vector competence studies often focus on Ochlerotatus triseriatus, though other Aedes species may contribute to transmission in some regions.