Health Advisory: Zika Testing

| May 30, 2017
mosquito

Action Requested

Know how to order appropriate Zika virus testing through commercial laboratories.

Background

Because testing for Zika virus is now widely available through commercial laboratories, testing for Zika virus at Washington State Public Health Laboratories is now limited to:

  • Patients for whom cost is a barrier to testing.
  • Infants with possible congenital exposure to Zika virus.

For Public Health Laboratories (PHL) testing, CDC testing criteria must be met and the test must be pre-approved by the Health Department. All infant testing should continue to be performed by PHL.

  • All other individuals should be tested using the normal mechanism for obtaining clinical commercial laboratory testing and following the CDC testing algorithm, except for infant testing.
  • Health Department approval is not required for commercial testing.
  • Zika virus testing is available through many commercial laboratories, including LabCorp, ARUP, Quest and Mayo.
  • The Health Department is available for consultation about determining whether possible Zika virus exposure occurred, choosing the correct testing algorithm and following up with patients who test positive.
  • Contact the Health Department for testing guidance and to report suspected Zika infection cases.

Important Reminders

  • Counsel women who are pregnant or planning to become pregnant to avoid travel to areas with Zika virus transmission risk and to avoid unprotected sex with sexual partners who have traveled to areas with CDC Zika travel notices.
  • Assess all pregnant women for possible Zika virus exposure at each prenatal care visit. Record travel history and sexual partner travel history at every visit and counsel pregnant women about the risk of Zika virus infection.
  • Counsel women with possible Zika virus exposure to wait at least eight weeks before trying to conceive, or at least six months if their male partner also had possible exposure to Zika virus.
  • Test every pregnant patient with possible exposure to Zika virus from:
    • Travel to an area with a CDC Zika travel notice.
    • Unprotected sex with someone who traveled to an area with a CDC Zika travel notice.
    • Travel to another area with possible Zika transmission risk and development of symptoms consistent with Zika virus disease within 14 days.

Zika Virus Test Ordering Guidance

If in doubt about whether testing is indicated, or which tests to order, contact the Health Department.

Testing should only be ordered for people with symptoms consistent with Zika virus disease and possible exposure, or for pregnant women with possible Zika virus exposure and their infants. Testing should not be used to rule out infection for pre-conception planning.

If a patient meets CDC testing criteria:

  • In general, order both an RT-PCR or NAA (on serum and urine) and an IgM ELISA (on serum).
  • As the length of time since last travel or sexual exposure or disease onset increases past 14 days, viral RNA in serum and urine declines and RT-PCR or NAA will be less useful. For patients seen more than two weeks after disease onset or last exposure, IgM ELISA should be ordered.
  • For pregnant women who test negative in the first two weeks after last travel or sexual exposure, collect a second serum specimen for IgM ELISA between two to 12 weeks after last exposure.
  • For patients with symptoms consistent with mosquito-borne disease, dengue and chikungunya testing should also be ordered.
  • A negative RT-PCR or NAA test never rules out Zika virus infection; order IgM ELISA on serum.
  • A positive IgM ELISA is preliminary evidence of Zika virus infection that should be confirmed by PRNT testing at CDC.
    • Laboratories will automatically send IgM positive, equivocal, or inconclusive specimens to CDC for PRNT testing.
    • Decisions about clinical management of IgM positive patients should wait for PRNT results.
  • If all or part of an exposure period occurred more than 12 weeks prior to specimen collection, infection in asymptomatic pregnant women cannot be ruled out. Contact the Health Department about testing at birth.
  • For infant testing or testing at the time of delivery, contact the Health Department.

Resources

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DOH Zika webpage for Healthcare Providers

CDC Zika webpage for Healthcare Providers

CDC testing algorithms: