Encephalitis is an acute infection and inflammation of the brain itself. This is incontrast to meningitis, which is an inflammation of the layers covering the brain.
Encephalitis is generally a viral illness. Viruses such as those responsible for causing cold sores, mumps, measles and chickenpox can also cause encephalitis. A certain family of viruses, the Arboviruses are spread by insects such as mosquitoes and ticks. The equine (meaning horse), West Nile, Japanese, La Crosse and St. Louis encephalitis viruses are all mosquito-borne. Although viruses are the most common source of infection, bacteria, fungi and parasites can also be responsible.
The illness resembles the flu and usually lasts for 2-3 weeks. It can vary from mild to life-threatening, and even cause death. Most people with a mild case can recover fully. Those with a more severe case can recover although they may have damage to their nervous system. This damage can be permanent.
- Age, season, geographic location, regional climate conditions and strength of the person's immune system play a role in development of the disease and severity of the illness.
- Herpes simplex (the virus causing cold sores) remains the most common virus involved in encephalitis in the United States and throughout the world.
- In the United States, there are 5 main viruses spread by mosquitoes: West Nile, Eastern equine encephalitis (EEE), Western equine encephalitis (WEE), La Crosse, and St. Louis encephalitis.
- The 1999 New York City outbreak of West Nile virus, spread by the Culexmosquitoes, has caused great concern as the virus continues to spread across the US.
- Venezuelan equine encephalitis is found in South America. It can be a rare cause of encephalitis in Southwestern United States, particularly Texas. The infection is very mild, and nervous system damage is rare.
- Japanese encephalitis virus is the most common arbovirus in the world (virus transmitted by blood-sucking mosquitoes or ticks) and is responsible for 50,000 cases and 15,000 deaths per year. Most of China, Southeast Asia, and the Indian subcontinent are affected.
The signs and symptoms of encephalitis are the same for adults and children:
- Signs and symptoms may last for 2-3 weeks, are flu-like, and can include 1 or more of the following:
- Sore throat.
- Stiff neck and back.
- Unsteady gait.
- Visual sensitivity to light.
- More severe cases may involve these signs and symptoms:
- Muscle weakness.
- Memory loss.
- Sudden impaired judgment.
- Poor responsiveness.
Encephalitis is usually a viral illness, which means that antibiotics are not used to treat it. The only available vaccine for prevention is for Japanese encephalitis.
- With the exception of herpes encephalitis, the mainstay of treatment is symptomrelief. People with encephalitis are kept hydrated with IV fluids while monitoring forbrain swelling. Anticonvulsants can be given for seizure control. Steroids have not been established as being effective.
- Herpes encephalitis can cause rapid death if not diagnosed and treated promptly. Therefore, medication is usually started when the doctor suspects herpes to be the diagnosis without waiting for the confirmatory results. The recommended treatment is acyclovir (Zovirax) given by IV for 2-3 weeks. Acyclovir-resistant herpes encephalitis can be treated with foscarnet (Foscavir). Liver and kidney functions are monitored through the course of medication.
- Currently, the use of ribavirin (Rebetol, Virazole) in the treatment of a child with La Crosse encephalitis is being studied.