Encephalitis, or inflammation of the brain tissue, is rare, affecting approximately 1 in 200,000 people each year in the United States. It is usually caused by one of several viruses, so it is often referred to as viral encephalitis.
Viral encephalitis may develop during or after infection with any of several viruses including enteroviruses, influenza, herpes simplex, measles, mumps, rubella, rabies, chicken pox, arboviruses (viruses transmitted by mosquitoes and other insects) such as West Nile virus, and others. Non-viral infections which can cause encephalitis are much less common and include certain bacteria, fungi, and parasites. In addition, some cancers or exposure to certain drugs or toxins may also cause encephalitis.
Symptoms include sudden fever, headache, vomiting, weakness, photophobia (abnormal sensitivity to light), mental changes (e.g. confusion or irritability), drowsiness, and unsteady gait or loss of balance. Severe complications can include loss of consciousness, seizures, and muscle paralysis.
Not in most cases. Enteroviruses can be spread from person to person but in most people either cause no symptoms at all, or a mild respiratory or diarrhea illness. There is no preventive treatment for contacts of patients with viral encephalitis.
Young children, the elderly, and those with a weak immune system are most vulnerable. However, encephalitis can occur in otherwise healthy persons.
Individuals with encephalitis are usually hospitalized for treatment. The specific treatment is determined by the cause of the illness. Some viral infections are treatable with medication, and all patients are treated with supportive care (nutrition, breathing assistance if necessary, etc) until they recover. The patient's chance of recovery depends on the specific cause of the illness and the severity of the inflammation in the brain and surrounding tissues and fluids.
The prognosis for viral encephalitis varies. Some cases are mild and patients recover fully. Other cases are more severe, and permanent impairment or death is possible. The acute phase of viral encephalitis may last for 1 to 2 weeks, with gradual or sudden resolution of fever and neurologic symptoms. Neurologic symptoms may require many months before full recovery, and patients may require rehabilitative services.
Last Updated: October 2000