Common Forms of Mosquito-Borne Arbovirus Encephalitis
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Eastern Equine Encephalitis
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Virus Family
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Text Continues Below
Togaviridae (genus Alphavirus)
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U.S. Geographic Areas
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Atlantic and Gulf coasts, in New England, and around the Great Lakes. States most affected are Florida, Georgia, Massachusetts, and New Jersey.
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Symptom Onset
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Symptoms appear 4-10 days following infection and can range from mild flu-like symptoms to full-blown encephalitis.
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Incidence and Mortality Rates
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The most serious of the US arboviruses and fortunately rare. Only 200 cases have been confirmed since 1964 with an average rate of 4 cases per year. Mortality rates are approximately 35-50%. Children are more likely to survive but also to suffer complications afterward.
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Age Risk Groups
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Adults over age 50 and children under age 15. |
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Western Equine Encephalitis
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Virus Family
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Togaviridae (genus Alphavirus)
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U.S. Geographic Areas
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Farming areas in western and central Plains and Rocky Mountain states west of the Mississippi.
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Symptom Onset
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5-10 days following infection.
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Incidence and Mortality Rates
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Very rare. There was only one case reported between 1995 and 2000. Mortality rate is 3 - 4%; 30% of survivors have complications afterward. Most severe in children, especially those younger than 1 year. Infants may suffer permanent neurological damage.
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Age Risk Groups
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Infants younger than 12 months. |
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St. Louis Encephalitis
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Virus Family
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Flaviviridae (genus Flavivirus)
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U.S. Geographic Areas
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Takes its name from an epidemic in St. Louis, but outbreaks have occurred in wider geographic areas, especially in midwestern and southeastern states, and can occur in rural or urban areas. As of 2000, the highest numbers of total cases have been reported in Texas (970), Illinois (695), Ohio (440), Indiana (368), and Florida (379).
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