Arbovirus Laboratory guidance
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. Request 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 persons
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 testing criteria:
Fee-exempt testing for arboviral infection (including JCV and POWV)
will be offered to clinicians whose patients meet one of the following
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-Barrι syndrome and no other
The local health department may request fee-exempt testing be
performed if the case-patient lacks insurance coverage or the ability to
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
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
Virus-specific IgM antibodies in CSF or serum but with no other
testing in the same or later specimen.
January 23, 2014