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Virology / Serology: Arbovirus

General Information

Diagnostic serologic assays are performed on serum and CSF suspected for Arbovirus. The Arbovirus panel includes Eastern Equine Encephalitis (EEE), Western Equine Encephalitis (WEE), St. Louis Encephalitis (SLE), LaCrosse Encephalitis (LAC), and West Nile Virus (WNV). Classical WNV fever is often associated with headache, lymphadenopathy, nausea, vomiting, and fatigue. WNV Central Nervous System (CNS) infection is associated with meningitis, encephalitis, meningoencephalitis, and/or acute flaccid paralysis resembling Guillian-Barre syndrome. All specimens received will be tested for IgG antibodies to EEE, WEE, LAC, SLE, and WNV and IgM antibodies to WNV and LAC by immunofluorescence (IFA) or enzyme immunoassay (EIA).

Serologic and molecular testing for chikungunya, Zika, and dengue viruses is now available at the NCSLPH.  Suspected cases should first be reported to the Communicable Disease Branch to receive approval for testing. All clinical and travel information, including date of onset, must be included on the test request form. Specimens from symptomatic patients with travel history collected <14 days post-illness onset will be tested first by RT-PCR. If RT-PCR is negative, these specimens will also be tested for the presence of IgM antibody by ELISA. Specimens from symptomatic travelers collected ≥14 days post-onset or asymptomatic travelers will receive IgM ELISA testing only. Additional testing may be performed for symptomatic or asymptomatic patients who are pregnant and have traveled to or are living in areas with active Zika transmission. All specimens with “Presumptive Positive” IgM ELISA results will be referred to CDC for confirmatory plaque reduction neutralization testing. Testing for chikungunya, Zika, and dengue will also be included with requests for Arboviral panel testing on patients with a history of travel to an endemic area. Urine and amniotic fluid may also be submitted for Zika molecular testing, but these specimen types must be submitted along with a paired serum specimen. Special requests for molecular testing on specimen types such as cord blood, placental tissue, or umbilical tissue can be arranged at CDC.

For more information about these viruses, go to http://www.cdc.gov/.

Specimen Collection and Identification

Only serum and CSF may be submitted for serologic testing. Clearly label each specimen vial with the patient's full first and last name, either SSN, date of birth or other unique identifier, and the date collected if paired sera are submitted. Complete a Special Serology Form #3445 (PDF, 113 KB) submission form specifying all required patient information and which infectious agents are suspected. Failure to supply the requested patient information (onset date, collection date(s), submitter name and address, signs/symptoms, travel history, vaccination history, etc.) may result in significantly delayed specimen testing. Tests must be requested by name. Nonspecific requests for "viral studies" or "viral serologies" will not be accepted. Consult with the laboratory if there is a question as to which test is appropriate.

The serodiagnosis of a current or recent infection generally requires the simultaneous testing of paired serum specimens, principally, acute and convalescent serum specimens. The acute serum should be collected no later than 3-5 days after the onset of illness. The convalescent serum should be collected 2-3 weeks after onset or at the time of hospital discharge, for confirmation of probable cases. Since paired sera are advised for all arboviral studies (except for chikungunya, Zika, and dengue viruses), it is to the advantage of both the submitter and this laboratory if the acute serum is stored frozen by the submitter until the convalescent serum is collected. Both serum samples may be submitted with one submission form.

Serological diagnosis of arboviral infection can be made by demonstrating a four-fold or greater rise in titer between acute and convalescent sera. Additionally, single "high" antibody titers to viral and rickettsial agents may be considered presumptive evidence of recent infection.

Antibody determinations on cerebrospinal fluid may be of value in diagnosing viral encephalitis and other central nervous system diseases. Cerebrospinal fluids for serologies should always be accompanied by a serum collected the same day.

Equine specimens for Arboviral testing should be submitted through the Rollins Animal Diagnostic Laboratory.

Shipment

For Arboviral panel testing, send the properly identified vials of patient sera and the completed DHHS form #3445 in the blue-colored specimen mailers labeled SPECIAL SEROLOGY. For detailed shipping instructions using the double mailers, see Packing Instructions Using Outer Baggie (PDF, 4.6 MB). Ship at ambient temperature by the State Courier or U.S. Mail. Specimens should be shipped immediately and should arrive in the laboratory within 48 hours of collection. Specimens may be shipped refrigerated or at ambient temperature. If transport to the laboratory is to be delayed, specimens can be refrigerated up to seven days or frozen.

For chikungunya, Zika, and dengue testing, send the properly identified specimen vials on cold packs or frozen. These specimens should be packaged and shipped as Category B infectious substances.

Serum transport tubes and blue colored specimen mailers are available through the NCSLPH online supply ordering system at this website. Special Serology Form #3445 (PDF, 113 KB) may be downloaded and printed from this website.

Reporting Procedure and Interpretation

Failure to detect a significant antibody response may be the result of a number of factors including improperly collected specimens, specimens collected too early or too late during the immune response, selection of the incorrect infectious agent for testing, or lack of sensitivity in the serological system being used.

The following chart lists the arboviral assays performed by this lab. A brief statement of the "normal" values for each assay is given under the heading "Negative Reference Range". The test method, specimen requirements, and turn-around-times are also listed for each assay performed.

Arboviral Assays
Test Test Method Negative Reference Range Specimen Requirement Turn-Around-Time
California Encephalitis (LAC), IgG IFA-Quant <1:16 2 mL serum/CSF; PSA 6 working days
LAC, IgM IFA-Quant
EIA-Qual
<1:16
Negative
2 mL serum/CSF; PSA 6 working days
Eastern Equine Encephalitis (EEE), IgG IFA-Quant <1:16 2 mL serum/CSF; PSA 6 working days
EEE, IgM IFA-Quant <1:16 2 mL serum/CSF; PSA 6 working days
St. Louis Encephalitis (SLE), IgG IFA-Quant <1:16 2 mL serum/CSF; PSA 6 working days
SLE, IgM IFA-Quant <1:16 2 mL serum/CSF; PSA 6 working days
Western Equine Encephalitis (WEE), IgG IFA-Quant <1:16 2 mL serum/CSF; PSA 6 working days
WEE, IgM IFA-Quant <1:16 2 mL serum/CSF; PSA 6 working days
West Nile Virus (WNV), IgG IFA-Quant
EIA-Qual
<1:16
Negative
2 mL serum/CSF; PSA 6 working days
WNV, IgM IFA-Quant
EIA-Qual
<1:16
Negative
2 mL serum/CSF; PSA 6 working days
Zika Virus (ZIK), IgM EIA-Qual Negative 2-5 mL serum 6 working days
Zika Virus (ZIK), PCR rRT-PCR Negative 2-5 ml serum/ CSF/Urine/ Amniotic Fluid/Whole Blood (EDTA) 6 working days
Chikungunya Virus (CHIK), IgM EIA-Qual Negative 2-5 mL serum 6 working days
Chikungunya Virus (CHIK), PCR rRT-PCR Negative 2-5 ml serum/ CSF/Urine/ Amniotic Fluid/Whole Blood (EDTA) 6 working days
Dengue Virus (DEN), PCR rRT-PCR Negative 2-5 ml serum/ CSF/Urine/ Amniotic Fluid/Whole Blood (EDTA) 6 working days
Dengue Virus (DEN), IgM EIA-Qual Negative 2-5 mL serum 6 working days

Abbreviations

  • EIA: Enzyme Immunoassay
  • IFA: Indirect Fluorescent Antibody
  • IgG: Immunoglobulin G
  • IgM: Immunoglobulin M
  • Quant: Quantitative
  • Qual: Qualitative
  • PSA: Paired Sera Advised

Additional Information

For additional information on West Nile virus and other arboviruses please visit:

Virology/Serology Information