La Crosse Encephalitis

Old tree with a deep hollow

La Crosse virus is spread to people by the bite of an infected mosquito. Most people infected with the virus do not have symptoms. Some people may develop severe disease, including encephalitis (inflammation of the brain). Severe disease occurs most often in children under 16 years of age. Most cases occur in the upper Midwestern, mid-Atlantic, and southeastern states. You can reduce your risk of infection by preventing mosquito bites.