La Crosse Encephalitis
Contact Info
Infectious Disease Epidemiology, Prevention and Control Division
651-201-5414
La Crosse Encephalitis Statistics
- The first case ever reported was in the early 1960’s in a Houston County, MN resident. The child died in a La Crosse, Wisconsin hospital, and the disease was subsequently named after this city.
- La Crosse encephalitis is found in southeastern Minnesota, especially in counties along the Mississippi River. A 2012 Stearns County case represented the farthest north and west that La Crosse encephalitis virus has been reported to date in the United States.
- The disease, which primarily affects children, is spread through the bite of infected Aedes triseriatus (Eastern Tree Hole) mosquitoes. Exposure to infected mosquitoes usually occurs in wooded or shaded areas, especially where water-holding containers (such as buckets, cans, or tires) provide good breeding habitat for the mosquito.
- Similar to other arboviruses, most La Crosse encephalitis cases occur later in the summer (July through September) when infected mosquito populations are at their highest level.
- In 2021, there were no reported cases of La Crosse encephalitis in Minnesota, which is consistent with the trend of fewer cases in the last few years. Since 1985, 145 cases have been reported from 22 Minnesota counties, primarily in the southeastern part of the state.
Maps and graphs:
- Reported Cases of La Crosse Encephalitis by Year, Minnesota, 1985-2021 (PDF)
Graph of reported cases of La Crosse encephalitis in Minnesota by year. - Reported Cases of La Crosse Encephalitis by County of Residence, Minnesota, 1985-2021 (PDF)
Map of reported cases of La Crosse encephalitis by county of residence.
Annual summaries:
- Arboviral Disease, 2019
Minnesota Department of Health Disease Control Newsletter Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2019- Arboviral Disease, 2018
- Arboviral Disease, 2017
- Arboviral Disease, 2016
- Arboviral Disease, 2015
- Arboviral Disease, 2014
- Arboviral Disease, 2013
- Arboviral Disease, 2012
- Arboviral Disease, 2011
- Arboviral Disease, 2010
- Arboviral Disease, 2009
- Arboviral Disease, 2008
- Arboviral Disease, 2007
- Arboviral Disease, 2006
- Arboviral Encephalitis, 2005
- Arboviral Encephalitis, 2004
- Arboviral Encephalitis, 2003
- Arboviral Encephalitis, 2002
- Arboviral Encephalitis, 2001
- Arboviral Encephalitis, 2000
National statistics
- CDC: La Crosse Encephalitis Epidemiology & Geographic Distribution
Maps, charts, tables, and reports from the CDC.