2005 - La Crosse Encephalitis

La Crosse Encephalitis

La Crosse encephalitis virus is endemic in Indiana. The disease is found primarily in the eastern United States where hardwood forests exist. The disease is maintained in nature in a cycle between the tree-hole mosquito, Ochlerotatus triseriatus, and small woodland mammals such as squirrels and chipmunks.

During the five-year period 2001-2005, 13 cases of La Crosse encephalitis were reported in Indiana with no reported cases in 2005. Figure 1 shows the number of reported cases per year from 2001-2005.

Clinically recognized infections occur mainly in children under 16 years of age. Symptoms include headache, fever, nausea, vomiting, drowsiness, and disorientation. Severe cases may result in seizures or coma. Cases are rarely fatal but may result in learning disabilities in recovered individuals. It has been estimated that for every symptomatic case there are 1,500 asymptomatic cases.

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