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Viral encephalitides
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Viral encephalitides

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Contributors: Daniel B. Fagbuyi MD, Alex Garza MD, MPH
Other Resources UpToDate PubMed


Mosquito-borne viral encephalitides include alphaviruses of the Togaviridae family such as the following:
Members of the Flaviviridae family such as the following:
And members of the Bunyaviridae family: California encephalitis group

Symptoms of the viral encephalitides range from none to mild to severe and may include 24–72 hours of spiking fever, chills, fatigue, myalgias (especially in the low back), severe headache, and photophobia. Nausea, vomiting, sore throat, conjunctival redness, and diarrhea may quickly follow the initial onset of illness. The disease may progress to central nervous system (CNS) disturbances such as seizures, ataxia, paralysis, paresis, delirium, coma, and death. Severe CNS involvement is more common in children.

The mortality rate of naturally occurring viral encephalitides is greater than 1% overall but may be as high as 20% after progression to severe encephalitis. EEE causes the most severe arbovirus encephalitis and has a high mortality rate.

The incubation period of viral encephalitides is typically 1-6 days. Viral reservoirs include horses, bats, birds, rodents, donkeys, mules, and tropical mammals from which the virus is transmitted via mosquitoes to humans and equines. Person-to-person transmission may be possible but has not been proven. 

Borna disease virus 1 (BoDV-1) may be a cause of severe encephalitis, and cases of transmission via organ transplantation have been observed.

Viral encephalitides are endemic to tropical regions of Central and South America, especially in rural areas. Eastern equine, western equine, St. Louis, and West Nile virus encephalitis are all endemic in North America.

Veterinarians, laboratory workers, tourists, military personnel, ranch workers, horseback riders, and residents of tropical areas are at higher risk for contracting viral encephalitides. Children are more susceptible to moderate or severe forms of the disease.

Note: Prevent mosquito bites in endemic areas with insect repellant and proper clothing. Vaccinate equines with TC-83 (a live attenuated virus).

Related topics: Encephalitis, Herpes simplex virus encephalitis


G05.3 – Encephalitis and encephalomyelitis in diseases classified elsewhere

34476008 – Viral encephalitis

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Last Updated: 10/31/2018
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Viral encephalitides
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Viral encephalitides : Chills, Diarrhea, Seizures, Fever, Severe headache, Vomiting, Photophobia, Biologic agent exposure, Myalgia
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