November 2, 2018
Jennifer Miller, 608-266-1683
Elizabeth Goodsitt, 608-266-1683

St. Louis Encephalitis Virus Reported in a Wisconsin Resident

The Wisconsin Department of Health Services (DHS) announced today that a confirmed human case of St. Louis encephalitis virus (SLEV) disease in a resident of Dane County, the first reported case in the state since 1981.

SLEV is related to West Nile virus (WNV) and, like WNV, is spread to people through the bite of an infected mosquito. SLEV is not transmitted person-to-person. SLEV is rare in Wisconsin, with only six human cases reported between 1964 and 2018 and no major outbreaks ever reported in the state.

Most people infected with SLEV will not have any symptoms. Those who do become ill may develop fever, headache, nausea, and fatigue that last for a few days. When symptoms do occur, they typically begin between five to 15 days after being bitten by an infected mosquito. In rare cases, SLEV can cause severe disease with symptoms such as stiff neck, disorientation, tremors, inflammation of the brain, and coma. Older adults and people with weakened immune systems are at an increased risk of severe disease from the virus.

There is no specific treatment for SLEV other than to treat symptoms. If you think you have SLEV or another mosquito-borne illness, contact your healthcare provider.

Mosquito activity has essentially ended for the year, so there is currently little to no risk of mosquito-borne illnesses in Wisconsin. There are, however, several things you can do next spring to minimize your exposure to mosquitoes and to eliminate mosquito breeding grounds. DHS recommends the following precautions any time when mosquitoes are active:

  • Limit time spent outside at dawn and dusk, when mosquitoes are most active.
  • Apply an insect repellent with DEET, IR3535, picaridin, or oil of lemon eucalyptus to exposed skin and clothing.
  • Make sure window and door screens are in good repair to prevent mosquito entry.
  • Prevent mosquitoes from breeding by removing stagnant water from items around your property, such as tin cans, plastic containers, flower pots, discarded tires, roof gutters, and downspouts.
  • Turn over wheelbarrows, wading pools, boats, and canoes when not in use.
  • Change the water in bird baths and pet dishes at least every three days.
  • Clean and chlorinate swimming pools, outdoor saunas, and hot tubs; drain water from pool covers.
  • Landscape to prevent water from pooling in low-lying areas, and trim tall grass, weeds, and vines since mosquitoes use these areas to rest during hot daylight hours.