Arboviral Encephalitis 2002

Indiana residents have traditionally been at risk for three arboviral encephalitis viruses:
1) eastern equine encephalitis (EEE), 2) St. Louis encephalitis (SLE), and 3) La Crosse encephalitis. A fourth, West Nile virus (WNV), was first identified in Indiana in 2001 in birds, mosquitoes, and horses. La Crosse encephalitis and West Nile virus will be addressed in separate sections of this report.

Eastern equine encephalitis is caused by a virus transmitted to humans and equines (horses) by infected mosquitoes and is maintained in a bird-mosquito cycle in fresh water swamps. In Indiana, the ecological system that supports the transmitting mosquito, Culiseta melanura, occurs only in the most north central counties. Horse and human cases occur sporadically. No human cases were reported in Indiana from 1998-2002.

St. Louis encephalitis (SLE) is also caused by a virus and is the most common mosquito-transmitted human pathogen in the United States. The virus is maintained in a bird-mosquito cycle involving the Culex species of mosquito. SLE occurs sporadically in Indiana. In 1975, a major epidemic occurred in Indiana, with over 300 reported cases. Few cases have been reported since then, and no cases were reported in Indiana from 1998-2002.

You can learn more about arboviral encephalitis by visiting the following Web site:
http://www.cdc.gov/ncidod/dvbid/arbor/index.htm.