Encephalitis Introduction & Overview

Encephalitis is an acute infection and inflammation of the brain leading to swelling of the brain. Viruses responsible for encephalitis are the family of Arboviruses, the equine, West Nile, Japanese, La Crosse and St. Louis encephalitis viruses. In addition, viruses that cause cold sores, mumps, measles, and chickenpox can also cause encephalitis.

In the US, five viruses i.e., West Nile, Eastern equine encephalitis (EEE), Western equine encephalitis (WEE), La Crosse and St. Louis encephalitis cause encephalitis. These viruses in the US are spread by blood sucking mosquitoes and ticks (1).

Other arboviruses causing encephalitis in different parts of the world include Murray Valley (endemic in Australia), Powassan (transmitted by ticks; occurs in Canada and the northern United States), tick-borne (occuring throughout Europe) and Venezuelan equine (common in Central and South America) (3).

Japanese encephalitis virus, most common arbovirus transmitted by mosquitoes or ticks, is the causal agent for 50,000 cases and 15,000 deaths annually. Japanese encephalitis virus affects major parts of China, Southeast Asia and the Indian subcontinent.

The infection ranges from mild to severe and in some cases can even be life threatening. Factors such as age, season, geographic location, regional climate conditions and strength of the person's immune system play a major role in the development of this disease and its severity (1).

Infection by a virus provokes the body’s immune system to fight off the virus and in the process may attack the nerves of the brain leading to a condition called Post Infectious or Autoimmune Encephalitis.

Inflammation of the meninges and the brain is called meningoencephalitis and inflammation of spinal cord and brain is called encephalomyelitis (2).

Conditions & Diseases: Brain & Nervous System

Encephalitis

Introduction & Overview