Treatment and Prevention


There is no specific treatment for La Crosse (LAC) encephalitis; clinical management is supportive. Patients with severe meningeal symptoms often require pain control for headaches and antiemetic therapy and rehydration for associated nausea and vomiting. Patients with encephalitis require close monitoring for the development of elevated intracranial pressure, seizures, and inability to protect their airway.


No LAC virus vaccines are available for use in humans. In the absence of a vaccine, prevention of LAC virus infection depends on personal protective measures to decrease exposure to infected mosquitoes. This includes using insect repellent, wearing long-sleeved shirts and pants, treating clothing and gear with 0.5% permethrin, and taking steps to control mosquitoes indoors and outdoors. More information about preventing mosquito bites can be found here.

LAC virus has been documented to cause disease in the same family during the same or different transmission seasons. Because of this, it is important to educate families who might have someone infected with La Crosse virus, on prevention methods.

  • Use an Environmental Protection Agency (EPA)-registered insect repellent and wear long-sleeved shirts and pants when outside.
  • Repair or install screens on windows and doors to keep mosquitoes out.
  • The mosquito that spreads LAC virus, Aedes triseriatus, prefers to lay its eggs in tree holes. You can reduce the number of mosquitoes around your home by filling tree holes that collect water.
  • LAC virus can survive the winter in mosquito eggs that will hatch into infected mosquitoes in the spring. Stop mosquitoes from laying eggs in or near water. Once a week, empty and scrub, turn over, cover, or throw out items that hold water.
    • Drill holes in tire swings so water drains out. Empty children’s wading pools and store on their side after use.