Saint Louis Encephalitis Virus Testing Information for Medical Professionals

West Nile Virus Information Report a Disease

Providers should consider Saint Louis encephalitis virus (SLEV) infection in their differential diagnosis of aseptic meningitis and encephalitis, particularly in patients over 50 years of age. Clinicians should consider obtaining tests for both SLEV and WNV if either one is considered.

The diagnosis of SLEV can be made by serology through SLEV-IgM antibody testing of CSF or serum. However, cross reactivity with WNV can be a problem. Serological tests for both SLEV and WNV are available at most commercial laboratories, and clinicians should consider obtaining both tests if one is considered. Given immunological cross-reactivity between WNV and SLEV, specimens positive for SLEV or WNV are routinely sent by LAC Department of Public Health (DPH) to the Viral and Rickettsial Diseases Laboratory (VRDL) at California Department of Public Health to distinguish between the two viruses.

Testing at LAC DPH Public Health Laboratory
LAC DPH Public Health Laboratory (PHL) provides SLEV-IgM testing in addition to WNV-IgM testing on serum samples from May to November. Select the Arbovirus Antibody Panel for testing. PHL does not charge the submitter for these services. NOTE: Testing at PHL from December to April requires consultation with the ACDC program (213-240-7941).

A standard laboratory submittal form must be completed and accompany the specimen(s). Each specimen must be labeled with the patient name and a second identifier (date of birth or medical record number), date of collection, and specimen type. Include a copy of previous test results and any pertinent patient history with the specimen including onset date. Send specimens by courier or overnight shipper using the appropriate transport conditions for the specimen type. Ship packages Monday-Thursday to avoid weekend deliveries. Frozen specimens should be shipped on dry ice.

SIGN UP: To receive the free weekly emailed West Nile Virus and Other Arboviral Diseases Report (published during WNV season) email: ACDC2@ph.lacounty.gov

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