St. Louis Encephalitis: Reporting and Surveillance

St. Louis encephalitis virus is a category II reportable condition in Wisconsin. Health care providers and laboratories should report to the patient's local public health department:

  • Electronically, through the Wisconsin Electronic Disease Surveillance System (WEDSS).
  • By calling the Bureau of Communicable Diseases at 608-267-9003.

Reporting should be completed within 72 hours upon recognition of a case. For more information, please visit our Disease Reporting page.

Watch our Arboviral Disease Surveillance Update Webinar to learn about arboviral diseases in Wisconsin, prevention and control, and surveillance and reporting information and updates. Given July 14, 2017.

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 Guidance Resources

DHS Surveillance Resources
Provider Resources

 Testing

Laboratory diagnosis of St. Louis encephalitis virus most often involves the detection of antibodies against St. Louis encephalitis virus in serum or cerebrospinal fluid (CSF). Testing for the presence of elevated IgM antibodies against St. Louis encephalitis virus and other domestic arboviruses using an arbovirus IgM antibody panel (includes testing for West Nile, St. Louis encephalitis, Jamestown Canyon, La Crosse encephalitis, Eastern equine encephalitis, and Powassan viruses) can be requested through the Wisconsin State Laboratory of Hygiene (WSLH). If St. Louis encephalitis virus infection is suspected, concurrent testing for other domestic arboviruses should be considered, since clinical features of these viruses overlap.

The WSLH arbovirus IgM antibody panel screens for evidence of infection through IgM antibody-capture enzyme-linked immunosorbent assay or microsphere immunoassay performed on serum or CSF. The WSLH will forward specimens with positive IgM results to CDC for confirmatory testing by plaque reduction neutralization test (PRNT).

The arbovirus IgM antibody panel is available at the WSLH fee-for-service or fee-exempt for qualifying patients. It is not required for patients' symptoms to meet the Division of Public Health (DPH) clinical criteria to submit serum of CSF specimens to the WSLH for fee-for-service arboviral screening.


DPH monitors for St. Louis encephalitis virus as part of our enhanced arbovirus surveillance. Testing for St. Louis encephalitis virus as part of a DPH investigation may be fee-exempt. Please contact a vectorborne disease epidemiologist at 608-267-9003 for fee-exempt approval.

Fee-exempt arboviral testing will be offered to clinicians whose patients meet ONE of the following criteria:

  • Request for confirmatory testing of positive IgM and IgG commercial test results (performed at laboratories other than the WSLH).
  • The patient has signs and symptoms of meningitis (fever, headache, and stiff neck) or encephalitis (fever, headache, and altered mental status ranging from confusion to coma), or acute flaccid paralysis (AFP) with no other laboratory diagnosis.
  • The patient has a diagnosis of Guillain-Barré syndrome and no other laboratory diagnosis.
  • The local health department may request fee-exempt testing be performed if the case-patient lacks insurance coverage or the ability to pay.

Instructions for collection and shipping of clinical specimens to WSLH:

  • Submit 3-7 mL of serum and/or >1mL of CSF in sterile screw-capped vials on cold packs using a WSLH kit #22 or equivalent within five days of collection. It is recommended that a paired serum specimen be submitted with a CSF specimen. Specimens should be triple packages as a Category B Biological Substance (include UN3373 label).
  • Fee-exempt testing submissions must include a WSLH Enhanced Wisconsin Arbovirus Surveillance form provided by a DPH vectorborne disease epidemiologist.
  • Fee-for-service testing submissions must include a WSLH CDD Requisition Form B. Please contact the WSLH Clinical Orders at 800-862-1088 or 608-224-4275 to obtain blank copies of WSLH CDD Requisition Form B and to order specimen shipping kits.
  • It is essential that the lab requisition form be as complete as possible, including patient name, city, date of birth, specimen type, submitting agency, onset date, signs and symptoms, and collection date. Note: Testing for St. Louis encephalitis virus may be delayed on specimens missing the above data until information is available.
  • Ship specimens with appropriate completed form to:

    Wisconsin State Laboratory of Hygiene
    2601 Agriculture Drive
    PO Box 7904
    Madison, WI 53718
    Customer Service: 800-862-1013

 Diagnosis

Clinical diagnosis of St. Louis encephalitis virus can be difficult since many of the signs and symptoms of St. Louis encephalitis virus are similar to other viral infections. A patient's clinical signs and symptoms and risk activities can help to inform a preliminary diagnosis prior to laboratory confirmation.

 Treatment

There is currently no treatment or vaccine for St. Louis encephalitis virus. Over-the-counter pain relievers may be given to relieve the symptoms. In severe cases, patients may need to be hospitalized to receive supportive treatment.

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Phone: 608-267-9003 | Fax: 608-261-4976

Last Revised: January 10, 2020