Encephalitis

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• Encephalitis Overview
• Encephalitis Causes
• Encephalitis Symptoms
• When to Seek Medical Care
• Exams and Tests
• Encephalitis Treatment
• Self-Care at Home
• Medical Treatment
• Next Steps
• Follow-up
• Prevention
• Outlook
• For More Information
• Web Links
• Multimedia
• Synonyms and Keywords
• Authors and Editors

Encephalitis Overview

Encephalitis is an acute infection and inflammation of the brain itself. This is in contrast 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 Culex mosquitoes, 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.