Laboratory Testing

IMPORTANT NOTICE: Updated Zika Testing Guidance

In March 2020, we updated our testing guidance for asymptomatic and symptomatic persons based on local and national trends. There is now increased scientific knowledge of the disease and the limitations of available tests.

  • Zika virus testing is no longer recommended for asymptomatic persons, regardless of travel history or pregnancy status.
    • Previously, DSHS recommended testing asymptomatic pregnant women by PCR if they:
      • Recently traveled to a Zika virus risk area outside Texas or their sexual partner had done so, or
      • Resided in Cameron, Hidalgo, Kinney, Maverick, Starr, Val Verde, Webb, Willacy, and Zapata counties.
    • DSHS continues to not recommend any Zika testing for asymptomatic, non-pregnant persons.
  • Test symptomatic pregnant women with possible Zika exposure using PCR only. Zika IgM testing is not recommended.*
    • Possible exposure to Zika includes:
      • Recent travel to or residence in a Zika virus risk area outside the US and its territories, or sexual exposure to a traveler to a risk area, or
      • Residence in Cameron, Hidalgo, Kinney, Maverick, Starr, Val Verde, Webb, Willacy, and Zapata counties.
    • Zika virus symptoms may include:
      • Rash
      • Fever
      • Conjunctivitis (red eyes)
      • Joint pain
    • Previously, DSHS recommended testing symptomatic pregnant women with Zika exposure by both PCR and IgM.
  • Zika testing is no longer recommended for symptomatic non-pregnant persons with exposure to a Zika risk area.
    • Evaluate these people for other possible infectious diseases, especially dengue virus, which causes similar symptoms and is a common infection in areas with a history of Zika transmission.
    • Many countries reported large dengue outbreaks recently, and dengue risk remains high in these areas.

*Zika IgM testing is still recommended alongside PCR for pregnant women with ultrasound evidence of fetal abnormalities consistent with Zika after possible Zika exposure.

The DSHS Austin Laboratory and many other Texas Laboratory Response Networks (LRNs) are performing the Trioplex Real-Time reverse transcriptase polymerase chain reaction (rRT-PCR) for Zika and the Zika virus-specific IgM Antibody Capture Enzyme-Linked Immunosorbent Assay (Zika MAC-ELISA). Please review the Chikungunya, Dengue, and Zika PCR and Serology Specimen Criteria guidance document (75 kb, PDF) (updated Dec. 16, 2016) to facilitate laboratory testing of individuals meeting the testing criteria. Specimens submitted to the DSHS Austin Laboratory must be accompanied by a G2-V form and a completed Chikungunya, Dengue, and Zika Testing Supplemental Information Form (65 kb, PDF) (updated Sept. 12, 2016). The plaque-reduction neutralization test (PRNT), used to confirm Zika virus infection in certain situations, is available at the U.S. Centers for Disease Control and Prevention (CDC) and some state laboratories.

On June 14, 2019, the Centers for Disease Control and Prevention provided detailed, updated guidance on appropriate testing and test result interpretation for individuals with Zika-compatible symptoms and exposure – refer to Dengue and Zika Virus Diagnostic Testing for Patients with a Clinically Compatible Illness and Risk for Infection with Both Viruses.

On May 31, 2017 the CDC released interim guidance on Zika virus antibody testing and interpretation of results. Because of the differences in recommended clinical management of Zika and dengue virus infections, and the risk of adverse pregnancy outcomes in women infected with Zika virus during pregnancy, a conservative approach to the interpretation of antibody test results is necessary to reduce the possibility of a missed diagnosis of either infection. The timing of IgM antibody testing and the thresholds of plaque reduction neutralization test (PRNT) have changed.

  • Based on earlier flavivirus research and limited preliminary data specific to Zika virus, the historical use of a 4-fold higher titer by PRNT might not discriminate between anti-Zika virus antibodies and cross-reacting antibodies in persons who have been previously infected with or vaccinated against a related flavivirus (i.e., secondary flavivirus infection).
  • Together with a positive or equivocal IgM to Zika or dengue virus:
    • A PRNT titer >10 will be interpreted as a evidence of infection with that specific flavivirus infection when the PRNT to the other flavivirus(es) tested is <10.
    • A PRNT titer <10 to a specific flavivirus will be interpreted as no evidence of infection with that virus.
    • If PRNTs are positive i.e., >10 to multiple flaviviruses, this will be interpreted as evidence of recent infection with a flavivirus.

CDC will continue to update this guidance as additional data becomes available. For more information about this guidance, visit Interim Guidance for Interpretation of Zika Virus Antibody Test Results .

Additional guidelines for healthcare providers are on the Health Professionals page.

If you are unsure whether your patient meets the recommended testing criteria for DSHS, please contact your local health department or DSHS public health region for assistance.