Mosquitoes can carry viruses that can cause serious disease in some individuals.
Residents are advised to take appropriate precautions to avoid mosquito bites. In most healthy individuals, infection with these viruses produces only mild symptoms, such as headache, fever, fatigue or muscle ache. Severe and potentially fatal illness can occur among infants and the elderly. In 1997, one death due to SLE was reported in a resident of Los Angeles County. Each summer throughout California, local mosquito and vector control districts conduct surveillance for mosquitoes and mosquito-borne viruses.