About La Crosse Encephalitis

La Crosse Encephalitis is a viral disease spread by infected mosquitoes. It is native to the upper Midwest and Appalachia, and was first diagnosed in La Crosse, Wisconsin in 1963.

The virus can cause symptoms including fever, headache, nausea, fatigue and vomiting. More severe effects, usually in children, can include seizures, coma, paralysis and lasting brain damage. The symptoms occur five to 15 days after being bitten.

People who spend time outside in woodland environments, especially children under age 16, are at an increased risk for La Crosse Encephalitis. There is no vaccine available, and treatment focuses on alleviating symptoms.

The life cycle of the La Crosse Encephalitis Virus is complex. The disease is carried by certain species of mosquitoes that breed in tree holes and containers in wooded areas. The virus is transmitted to chipmunks and squirrels by mosquitoes, and in turn transmitted back to the mosquito population as other mosquitoes feed on the squirrels. Occasionally, these mosquitoes will transmit the disease to humans.

Prior to 2002, La Crosse Encephalitis was the most common mosquito-borne disease in this country. There are an average of 75 cases per year in the 27 states where the virus is found. Historically, Ohio accounts for approximately 30 percent of the total cases each year.

The best way to reduce your risk of contracting La Crosse Encephalitis is to reduce your exposure to mosquito bites. Eliminating small containers that fill with water (trash, flower pot saucers, scrap tires, etc.) can reduce the number of mosquitoes in your yard. Following the guidelines about personal protection can further reduce your exposure to mosquito bites and protect you from La Crosse Encephalitis and other mosquito-borne diseases.