St. Louis Encephalitis

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St. Louis Encephalitis Virus
Virus classification
Group: Group IV ((+)ssRNA) Family: Flaviviridae Genus: Flavivirus Species: St. Louis Encephalitis Virus

St. Louis Encephalitis is a disease caused by the mosquito borne St. Louis Encephalitis virus. St. Louis encephalitis virus is related to Japanese encephalitis virus. This disease mainly affects the United States. Occasional cases have been reported from Canada and Mexico.

The name of the virus goes back to 1933 when within five weeks in autumn an encephalitis epidemic of explosive proportions broke out in the vicinity of St. Louis, Missouri and the neighboring St. Louis County.^[1] Over 1,000 cases were reported to the local health departments and the newly constituted National Institute of Health was appealed to for epidemiological and investigative expertise. The previously unknown virus that caused the epidemic was isolated by the NIH team first in monkeys and then in white mice. ^[2]

Mosquitoes, from the genus Culex, become infected by feeding on birds infected with the St. Louis encephalitis virus. Infected mosquitoes then transmit the St. Louis encephalitis virus to humans and animals during the feeding process. The St. Louis encephalitis virus grows both in the infected mosquito and the infected bird, but does not make either one sick. Only infected mosquitoes can transmit St. Louis encephalitis virus. Once a human has been infected with the virus it is not transmissible from that individual to other humans.

The majority of infections result in mild illness, including fever and headache. When infection is more severe the person may experience headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, occasional convulsions and spastic paralysis. Fatality ranges from 3-30%, aged people are more likely to have a fatal infection.

Human incidence of St. Louis encephalitis in the United States, 1964-1998

In the United States an average of 128 cases of St. Louis encephalitis are recorded annually. In temperate areas of the United States, St. Louis encephalitis cases occur primarily in the late summer or early fall. In the southern United States where the climate is milder St. Louis encephalitis can occur year round.

There is no vaccine or any other treatments specifically for St. Louis encephalitis virus.

[edit] References

• Centers for Disease Control and Prevention. CDC Answers Your Questions About St. Louis Encephalitis

[edit] External links

• Encephalitis Global Inc. Offering information and support to encephalitis survivors, caregivers and loved ones.

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