In addition to WNV, other insect-borne viruses (arboviruses) that can cause encephalitis in humans exist in Michigan. Three of these are the mosquito-borne viruses: St. Louis encephalitis virus (SLE), La Crosse encephalitis virus (LAC), and Eastern Equine encephalitis virus (EEE). Another is a tick-borne virus called Powassan. The Michigan Department of Agriculture has had a long-standing surveillance system for detection of SLE and EEE in birds, mosquitoes, and horses. Sporadic human cases of these mosquito-borne viruses can occur each year in Michigan as well. In contrast, encephalitis caused by Powassan virus had never been diagnosed in Michigan prior to 2002.

     As a result of the intensive surveillance to detect WNV in 2002, 21 cases of other arbovirus infections were detected in Michigan citizens that year, including 11 cases of LAC, 6 cases of EEE, 3 cases of SLE, and 1 case of Powassan virus. 

     EEE is an arbovirus other than WNV that can infect horses in Michigan. Vaccines are available to protect horses from WNV and EEE in Michigan.

Link to 2002-2008 Surveillance maps for other arboviruses in Michigan

Link to CDC's Webpage on Other Arboviruses