Which types of encephalitis are caused by mosquito bites?

Eastern equine encephalitis (EEE), while a relatively rare condition in the United States, is one of the more serious conditions that a person can get from a mosquito bite. Roughly 30% of people who become infected do not survive. Usually, its symptoms appear three to 10 days after a bite, and signs include fever, headache, nausea, vomiting, abdominal pain, light sensitivity, weakness, confusion, seizures and loss of consciousness.

La Crosse encephalitis virus (LCAV) occurs most often in the midwestern, mid-Atlantic and southeastern states. The infection can become serious when left untreated, sometimes resulting in dysfunction of the nervous system. It rarely results in death. Symptoms of LCAV include fever, headache, nausea, vomiting and fatigue.

Despite its regional name, Saint Louis encephalitis virus (SLEV) occurs throughout most of the country. Upon infection, many people are initially asymptomatic. Mild cases usually include a headache and fever, while more severe infections cause headache, extreme fever, stiffness in the neck, disorientation, coma, tremors, convulsions and paralysis.