A severe inflammation of the brain, encephalitis is usually caused by a mosquito-borne or, in some areas, a tick-borne virus. Viruses transmitted by arthropods are arboviruses (arthropod-borne). Transmission by means other than arthropod bites may occur through ingestion of infected goat’s milk and accidental injection or inhalation of the virus. Eastern equine encephalitis may produce permanent neurologic damage and is commonly fatal.

In encephalitis, intense lymphocytic infiltration of brain tissues and the leptomeninges causes cerebral edema, degeneration of the brain’s ganglion cells, and diffuse nerve cell destruction.


Encephalitis generally results from infection with arboviruses specific to rural areas. In urban areas, it’s most frequently caused by enteroviruses (coxsackievirus, poliovirus, and echovirus).

Other causes include herpesvirus, mumps virus, human immunodeficiency virus, adenoviruses, and demyelinating diseases after measles, varicella, rubella, or vaccination.

Between World War I and the Depression, a type of encephalitis known as lethargic encephalitis, von Econ-omo’s disease, or sleeping sickness occurred with some regularity. The causative virus was never clearly identified, and the disease is rare today. Even so, the term sleeping sickness persists and in many cases is mistakenly used to describe other types of encephalitis as well. The most recent outbreak of mosquito-borne encephalitis was West Nile encephalitis.

Signs and symptoms

All viral forms of encephalitis have similar clinical features, although certain differences do occur.

Usually, the acute illness begins with sudden onset of fever, headache, and vomiting and progresses to include signs and symptoms of meningeal irritation
(stiff neck and back) and neuronal damage (drowsiness, coma, paralysis, seizures, ataxia, and organic psychoses). After the acute phase of the illness, coma may persist for days or weeks.

Jun 16, 2016 | Posted by in GENERAL & FAMILY MEDICINE | Comments Off on Encephalitis

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