Clinical Testing and Diagnosis for Zika Virus Disease

Key points

  • Diagnostic testing for Zika virus infection and disease can be accomplished using both molecular and serologic methods.
  • Zika and dengue viruses share a similar global geographic distribution and cause infections with similar clinical presentations. Patients with suspected Zika virus infection also should be evaluated for possible dengue.
  • Contact your state health department for more information or to facilitate testing.
Zika diagnosis image with a woman being examined by a doctor

General testing information

Nucleic acid amplification test, or NAAT, is a generic term referring to all molecular tests used to detect viral genomic material. NAAT assays are the preferred method of diagnosis because they can provide confirmed evidence of infection. Despite the specificity of molecular testing, false-positive NAAT results have been reported.

Because of the short period and low level of Zika virus RNA in serum, a negative NAAT does not exclude recent Zika infection. For this reason, Zika virus immunoglobulin (Ig) M antibody testing is recommended in certain situations. IgM generally is detectable starting in the first week after onset of symptoms and persists months to years. IgM testing is complicated by cross-reactive antibodies to other flaviviruses, which might make conclusive determination of which flavivirus is responsible for the person's recent infection difficult. False-positive results are more common with IgM than NAAT and can occur due to non-specific reactivity or cross-reactivity with other flaviviruses.

Plaque reduction neutralization tests (PRNT) measure virus-specific neutralizing antibody titers. PRNTs may resolve false-positive IgM antibody results caused by non-specific reactivity and help identify the infecting virus. However, due to cross-reactivity, PRNT might not discriminate between flaviviruses antibodies, especially following secondary flavivirus infection.

For infant diagnosis, PRNT cannot distinguish between maternal and infant antibodies in specimens collected from infants at or near birth. Based on what is known about other congenital infections, maternal antibodies are expected to become undetectable by 18 months of age and might become undetectable earlier.

Resource

Dengue and Zika Virus Diagnostic Testing for Patients with a Clinically Compatible Illness and Risk for Infection with Both Viruses

Below is a summary of CDC's Zika testing guidance. It will be updated as needed to address the epidemiology of Zika virus. Healthcare providers are encouraged to contact their local, state, or territorial health departments for guidance on Zika testing and submitting specimens in their respective states.

Asymptomatic pregnant patient

Lived in or traveled to the United States and its territories during pregnancy

  • Because no confirmed cases of Zika virus disease have been detected in the United States and its territories since 2018, routine Zika virus testing is not recommended.

Traveled to an area with an active CDC Zika Travel Health Notice during pregnancy

Traveled to an area with current or past Zika virus transmission outside the United States and its territories during pregnancy

Symptomatic pregnant patient

Lived in or traveled to an area with an active CDC Zika Travel Health Notice during pregnancy

OR had sex during pregnancy with someone living in or with recent travel to an area with an active CDC Zika Travel Health Notice

  • Specimens should be collected as soon as possible after onset of symptoms up to 12 weeks after symptom onset.
  • Perform dengue and Zika virus NAAT and IgM testing on a serum specimen and Zika virus NAAT on a urine specimen.
  • If Zika NAAT is positive and the Zika IgM is negative, repeat NAAT test on newly extracted RNA from same specimen to rule out false-positive results.
  • If both dengue and Zika virus NAATs are negative but either IgM antibody test is positive, confirmatory PRNTs should be performed against dengue, Zika, and other flaviviruses endemic to the region where exposure occurred.
  • Resource: CDC Travel Health Notices

Lived in or traveled to an area with current or past Zika virus transmission during pregnancy

  • Specimens should be collected as soon as possible after onset of symptoms up to 12 weeks after symptom onset.

  • Perform dengue and Zika virus NAAT on a serum specimen and Zika virus NAAT on a urine specimen.
  • If Zika NAAT is positive, repeat test on newly extracted RNA from same specimen to rule out false-positive results.
  • Perform IgM testing for dengue only.
  • If dengue NAAT or IgM test is positive, this provides adequate evidence of dengue infection, and no further testing is indicated.
  • Resource: Areas with current or past Zika virus transmission

Had sex during pregnancy with someone living in or with recent travel to an area with current or past Zika virus transmission

  • Specimens should be collected as soon as possible after onset of symptoms up to 12 weeks after symptom onset.

Interim Guidance for Health Care Providers Caring for Pregnant Women with Possible Zika Virus Exposure—United States (Including U.S. Territories), July 2017

Read more about CDC's shared decision-making model for testing and screening pregnant women for Zika virus infection.

Pregnant patient having a fetus with prenatal ultrasound findings consistent with congenital Zika virus infection

Lived in or traveled during pregnancy to an area with an active CDC Zika Travel Health Notice or current or past Zika virus transmission

OR had sex during pregnancy with someone living in or with recent travel to an area with an active CDC Zika Travel Health Notice or current or past Zika virus transmission

  • Zika virus NAAT and IgM testing should be performed on serum and NAAT on urine.
  • If the Zika virus NAATs are negative and the IgM is positive, confirmatory PRNTs should be performed against Zika and dengue.
  • If amniocentesis is being performed as part of clinical care, Zika virus NAAT of amniocentesis specimens should also be performed and results interpreted within the context of the limitations of amniotic fluid testing.
  • Testing of placental and fetal tissues may also be considered.
  • Resources: CDC Travel Health Notices and Areas with current or past Zika virus transmission

Keep Reading: Collecting and Submitting Placental and Fetal Tissue Specimens for Zika Virus Testing

Symptomatic non-pregnant patient

Living in or with recent travel to the United States and its territories

  • Because no confirmed cases of Zika virus disease have been detected in the United States and its territories since 2018, routine Zika virus testing is not recommended.

    Living in or with recent travel to an area with an active CDC Zika Travel Health Notice or current or past Zika virus transmission outside the United States and its territories

    • Dengue and Zika virus NAATs should be performed on serum collected ≤7 days after symptom onset. A positive NAAT result typically provides evidence of acute infection.
    • Perform dengue and Zika virus IgM antibody testing on NAAT-negative serum specimens and serum collected >7 days after onset of symptoms.
    • If either dengue or Zika virus IgM antibody testing is positive, and definitive diagnosis is needed for clinical or epidemiologic purposes, confirmatory PRNTs should be performed against dengue, Zika, and other flaviviruses endemic to the region where exposure occurred.
    • Resources: CDC Travel Health Notices and Areas with current or past Zika virus transmission

    Asymptomatic non-pregnant patients

    Testing for dengue or Zika viruses is not recommended for this group.

    Infant with possible congenital Zika virus infection

    With a mother with possible Zika virus exposure during pregnancy

    • Collect specimens as soon as possible after birth.
    • Zika virus NAAT and IgM testing should be performed on infant serum and NAAT on infant urine.
    • If cerebrospinal fluid (CSF) is obtained for other purposes, NAAT and IgM antibody testing should be performed on CSF.
    • If the infant's serum is IgM non-negative and NAAT negative, but PRNT was not performed on the mother's serum, PRNT for Zika and dengue viruses should be performed on the infant serum.
    • Perform PRNT on a sample collected from an infant aged 18 months or older whose initial sample collected at birth was IgM non-negative and neutralizing antibodies were detected by PRNT in either the infant's or mother's sample.

    Update: Interim Guidance for the Diagnosis, Evaluation, and Management of Infants with Possible Congenital Zika Virus Infection—United States, October 2017

    Information for healthcare providers on caring for infants with possible congenital Zika virus infection.

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    Content Source:
    National Center for Emerging and Zoonotic Infectious Diseases (NCEZID)