What are the diagnostic tests for Zika virus (Zika virus) infection?

From the Guidelines

To test for Zika virus, a healthcare provider should order a PCR test to detect viral RNA within the first week of symptoms or an antibody test after the first week, considering recent travel to areas where Zika is common or sexual contact with someone who may have been infected. When testing for Zika virus, it is essential to consider the timing of symptom onset and the type of test to be performed. According to the Centers for Disease Control and Prevention (CDC) guidelines 1, for nonpregnant persons with a clinically compatible illness, dengue and Zika virus NAATs should be performed on serum collected ≤7 days after symptom onset. Some key points to consider when testing for Zika virus include:

• Informing the doctor about any symptoms experienced, such as fever, rash, joint pain, or red eyes
• Mentioning recent travel to areas where Zika is common or sexual contact with someone who may have been infected
• Understanding that pregnant women with possible exposure should be tested even without symptoms due to risks to the developing fetus
• Recognizing that Zika testing is crucial for those at risk, especially pregnant women or those planning pregnancy, as the virus can cause serious complications, including birth defects like microcephaly
• Being aware that most people with Zika have mild symptoms or none at all, making testing essential for early detection and prevention of complications. The CDC guidelines also recommend that for symptomatic pregnant women, serum and urine specimens should be collected as soon as possible within 12 weeks of symptom onset for concurrent dengue and Zika virus NAATs and IgM antibody testing 1. Additionally, positive IgM antibody test results with negative NAAT results should be confirmed by neutralizing antibody tests when clinically or epidemiologically indicated, including for all pregnant women 1. It is also important to note that the interpretation of test results should consider the epidemiology of viruses known to be circulating at the location of exposure and clinical findings 1. Overall, testing for Zika virus requires a comprehensive approach, considering the patient's symptoms, travel history, and risk factors, as well as the type and timing of tests to be performed.

From the Research

Testing Methods for Zika Virus

• The detection of viral-RNA by molecular methods, such as real-time reverse transcription-polymerase chain reaction (rRT-PCR) 2, 3, 4
• Detection of ZIKV-specific immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies by serologic tests, including enzyme-linked immunosorbent assays (ELISAs) 2, 3, 5, 6
• Plaque reduction neutralization test (PRNT) for confirmation of positive IgM results, especially in pregnant women 2, 5, 6

Sample Collection

• Zika virus may be detected in various bodily fluids, including:
  • Blood (whole blood, serum, plasma) 2, 4
  • Urine 2, 3
  • Saliva 2
  • Cerebrospinal fluid (CSF) 2
• The virus may be detected in urine for a longer period, up to 15-20 days from the onset of symptoms 2

Interpretation of Test Results

• A positive rRT-PCR result confirms Zika virus infection, but a negative result does not exclude infection 3
• Serologic test results can be difficult to interpret due to cross-reactivity with other flaviviruses 3, 5, 6
• The results of Zika and dengue virus testing will guide clinical management 3