Specimens should be tested using an arboviral panel because arboviruses have similar clinical symptoms and serologic testing often results in cross-reactive antibodies among agents. Arboviral panel testing should include WNV, SLEV, LACV, EEEV, and WEEV when there is clinical suspicion of arboviral disease, rather than requesting testing of individual virus agent. Requests for other arboviruses (JCV, POWV), including travel-related arboviruses (DENV, CHIKV), will be forwarded to the Centers for Diseases Control and Prevention (CDC) for testing. Powassan virus should be added to the arboviral panel test if patient exhibits signs and symptoms including confusion, memory loss, speech difficulty, altered mental status, encephalitis or meningitis.
All positive arboviral specimens tested by a commercial laboratory should be forwarded to the Wisconsin State Laboratory of Hygiene (WSLH) for the confirmatory arboviral panel test. The WSLH performs a combination of tests including IgM capture enzyme immunoassays (IgM CEIA) and Microsphere Immunoassay (MIA) for IgM antibodies performed on serum and cerebrospinal fluid (CSF). In addition, the WSLH will forward positive samples to CDC for confirmatory testing by Plaque Reduction Neutralization Test (PRNT).
Specific IgM antibodies to most arboviruses are usually detectable within 10 days after onset of illness and can persist up to at least one year. Positive IgM antibody to an arboviral agent may indicate a current infection, and confirmation testing should be performed. Specimen collected within 10 days of illness showing a negative IgM result should be repeated with a convalescent sample to rule out infection.
Specific IgG antibodies to arboviruses are usually detectable within 10 days of onset of illness and can persist throughout a person's lifetime. Thus, a positive IgG and a negative IgM in a sample collected after 10 days may indicate a previous infection at some point in time. Positive results from a single serologic test can be misleading because serologic cross-reactivity often occurs between closely related arboviruses. A convalescent sample should be collected within 2-4 weeks after onset of illness for confirmatory testing.
The WSLH offers arboviral testing for fee-for-service. Meeting clinical criteria is not required to submit serum or CSF specimens to the WSLH for fee-for-service arboviral screening.
Testing for any of the arboviral agents listed above as part of the Division of Public Health investigation may be fee-exempt. Please contact the Vectorborne Disease Epidemiologist at 608-267-0249 for fee-exempt approval.
Fee-exempt approval testing criteria
Fee-exempt testing for arboviral infection (including JCV and POWV) 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.
Collection and shipping of clinical specimens to the WSLH
- Specimens submitted to the WSLH for approved fee-exempt testing must include the WSLH - Enhanced Wisconsin Arbovirus Surveillance Form provided by the Vectorborne Epidemiologist.
- Specimens submitted for fee-for-service testing must use the WSLH CDD Requisition Form B. Please contact the WSLH-Clinical Stock Orders for ordering of kits and WSLH CDD Requisition Form B at 1-800-862-1088 or 608-265-2966.
- At least 3-7 mls of serum and/or U>U1ml of CSF in sterile screw-capped vials should be submitted on cold packs.
Note: It is essential that the lab requisition forms be as complete as possible, including the patient name, city, date of birth, specimen type, submitting agency, onset date, signs and symptoms, collection date, and travel history. Testing may be delayed on specimens with laboratory forms missing the above requested data.
Test result interpretation
- Isolation of virus from or demonstration of specific viral antigen or nucleic acid in tissue, blood, CSF, or other body fluid,
- Fourfold or greater change in virus-specific quantitative antibody titers between acute (within 2 weeks after onset date) and convalescent sample (2-4 weeks after onset date),
- Virus-specific immunoglobulin M (IgM) antibodies in serum by antibody-capture enzyme immunoassay (MAC-ELISA)
confirmed by demonstration of virus specific neutralizing antibodies in the same or later specimen (PRNT),
- Virus-specific IgM antibodies in CSF and a negative result for other arbobvirus IgM antibodies in CSF endemic to the region where exposure occurred.
- Virus-specific IgM antibodies in CSF or serum but with no other testing in the same or later specimen.
Diep Hoang Johnson
Vectorborne Disease Epidemiologist
Wisconsin Division of Public Health
Bureau of Communicable Diseases