2000 Indiana Report of Infectious Diseases

Arboviral Encephalitis

View CDC's Arboviral Encephalitides Page


Indiana had 2 reported cases of LaCrosse encephalitis in 2000.  Both cases occurred in males, one aged 9 and the other age 10.  LaCrosse encephalitis is primarily diagnosed in children younger than age 16.  From 1996 to 2000, Indiana had a total of 6 reported cases.  The number of inapparent cases far exceeds the number of apparent cases where serological surveys have been accomplished.

LaCross encephalitis is endemic in several areas of the state (Allen and surrounding counties, Decatur, Ripley, Jackson, and Jennings Counties) but may occur in other counties as well. The virus cycles between the tree-hole mosquito, Aedes triseriatuis, and small mammals, with squirrels and chipmunks serving as the primary host. While the mosquito prefers tree holes as a breeding site, it will breed in artificial containers such as tires, cans, or other containers capable of holding rainwater. Eliminating breeding sites and using mosquito repellents will control the virus.

Prior to December 2000, Indiana citizens have been at risk for infection with Eastern Equine Encephalitis (EEE), Western Equine Encephalitis (WEE), and St. Louis Encephalitis (SLE). None of these diseases has been confirmed in Indiana from 1996 to 2000.