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WNV Healthcare Provider Information

Commercial laboratory tests for West Nile virus by serology (IgM capture ELISA) or polymerase chain reaction are now available. Any patient testing positive for West Nile virus at a commercial laboratory should be reported to the local health department. For reporting purposes, confirmatory testing at the Illinois Department of Public Health (IDPH) or the U.S. Centers for Disease Control and Prevention is typically required by IDPH for validation of commercial laboratory tests that are positive for West Nile virus.

Testing Guidelines

  • Diagnostic testing for WNV is generally NOT recommended for individuals with non-specific "flu-like" symptoms in the outpatient setting. There are many causes of these non-specific symptoms and testing for WNV would be non-productive for the majority of patients.
  • Serum and cerebrospinal fluid (CSF) from all patients with encephalitic syndromes or aseptic meningitis should be sent to the Illinois Department of Public Health (IDPH) laboratory for free arbovirus testing. Acute serum and CSF will be tested for IgM antibody against WNV and St. Louis encephalitis (SLE) and, when a patient is 18 years of age or younger, California (LaCrosse) encephalitis (LAC) testing will also be performed. Specimens should be sent to the Illinois Department of Public Health Virology Laboratory, 2121 West Taylor Street, Chicago, Illinois 60612. The cost of shipping will be the responsibility of the submitter.
  • WNV testing should also be considered in the setting of other neurologic syndromes, especially severe muscle weakness. Approximately 10 percent of patients in the 1999 New York outbreak had complete flaccid paralysis and were originally suspected to have Guillain-Barre syndrome.
  • In order to submit specimens from patients with symptoms consistent with West Nile virus infections, a link to the IDPH Specimen Requisition Form is provided; this form must accompany submitted specimens.
  • Laboratory testing for WNV is available through the IDPH laboratory from May 15 to October 31 (or until 2 weeks after the first killing frost).