These viruses cause no harm to their arthropod vehicle, but may result in a systemic illness involving neurological signs in horse and man. California Equine Encephalitis is spread by infected mosquitoes. Most reported cases occur during the warm summer months when mosquito population is high. Everyone is susceptible to infection by CEE but the elderly and the young are the population most greatly affected. Most infections go unnoticed.
Some infections are mild - headache and fever.
Permanent brain damage may result with severe infections. Therapy is aimed at relieving the symptoms. Horses acquire CEE through mosquito bites. Young non-vaccinated horses are at greatest risk. The disease usually presents in summer when mosquito numbers are increased.