La Crosse Encephalitis 2004

Table 1. La Crosse Encephalitis Cases by Race and Sex, Indiana, 2004

  2004 2000-2004
Cases Rate* Cases
Total 1 0.02 15
   White 1 0.02 10
   Black 0 0 1
   Other 0 0 1
   Not Reported 0 - 3
   Male 1 0.03 11
   Female 0 0 4
   Not Reported 0 - 0

*Rate per 100,000 population based on the U.S. Census Bureau’s population data as of July 1, 2004

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 2000-2004, 15 cases of La Crosse encephalitis were reported in Indiana with 1 reported case in 2004. Figure 1 shows the number of reported cases per year from 2000-2004.

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.

You can learn more about La Crosse encephalitis by visiting the following Web site: