Q: What is La Crosse encephalitis?

A: The La Crosse virus is spread by infected mosquitoes. Most people don’t have symptoms, but some rarely develop encephalitis, or an inflammation of the brain that can be life-threatening.

Q: How many cases of La Crosse encephalitis are reported each year?

A: About 80 to 100 cases are reported nationwide each year, with roughly a quarter of cases (about 20) occurring in Ohio.

Q: Who’s at risk?

A: Anyone who is bitten by a mosquito in an area where the virus is circulating can contract the virus. The greatest risk is for people who live, work or spend time in wooded areas, where the “treehole mosquito” (Aedes trisertiatus) that spreads the disease lives. Severe disease most commonly occurs in children younger than 16.

Q: How soon after getting bitten by an infected mosquito do people get sick?

A: It takes five to 15 days to develop symptoms.

Q: What are the symptoms of La Crosse encephalitis?

A: Initial symptoms for those who become ill include fever, headache, nausea, vomiting and tiredness. Symptoms of severe disease include seizures, coma and paralysis.

Q: How is La Crosse encephalitis treated?

A: No medication exists to treat the viral disease. Severe illnesses are treated with supportive therapy, which can include hospitalization, respiratory support, IV fluids and prevention of secondary infections.

Q: Can it be prevented?

A: A vaccine doesn’t exist, but people can take these steps to prevent mosquito bites. Use insect repellent containing DEET, piracidin, IR3535 or oil of lemon eucalyptus on clothing and exposed skin. Wear long sleeves and pants if possible. Eliminate mosquito breeding areas by emptying standing water from flower pots, buckets, barrels, children’s swimming pools and other containers. Fill treeholes in and around your yard to eliminate the mosquito’s preferred breeding ground. Have secure, intact screens in windows and doors to keep out mosquitoes.

Sources: U.S. Centers for Disease Control and Infection; Ohio Department of Health