Various laboratory tests are available to identify the Zika virus. Although clinical symptoms and an individual's travel and exposure history may provide clues as to a possible Zika virus infection, the most accurate means to diagnose a possible Zika virus infection is by the use of laboratory tests to identify the virus in the individual. Currently, there are three types of laboratory tests for the identification of the Zika virus:
- Real-time reverse transcription-polymerase chain reaction (rRT-PCR) for measuring Zika virus RNA in serum and urine.
- The Zika IgM antibody capture enzyme-linked immunosorbent assay (Zika MAC-ELISA) for the detection of Zika virus IgM antibodies in serum.
- Plaque reduction neutralization test (PRNT) to confirm the presence of Zika virus specific antibodies.
Note: More information on the three types of Zika virus tests will be presented in other sections of this course.
During the course of the disease, Zika virus-specific IgM and neutralizing antibodies typically develop toward the end of the first week of illness. Moreover, the IgM levels can vary, but usually IgM levels are positive beginning near day four after the presentation of symptoms and the presence of IgM antibodies will continue for about 12 weeks
The CDC recommends that if rRT-PCR testing for Zika virus is negative on serum and urine, then serum IgM antibody testing for Zika, dengue, and chikungunya virus infections should be performed. Moreover when serum samples are collected at 14 days or greater after symptom onset and there are no earlier samples collected, CDC recommends that testing should be performed for anti-Zika virus, anti-dengue virus, and anti-chikungunya virus IgM antibodies.
rRT-PCR measures the Zika virus RNA and is often employed early in the course of the infection. It should be performed on serum collected during first two weeks after symptoms appear. rRT-PCR should also be performed on urine samples matched to patient serum specimens collected less than 14 days after symptom onset. Typically, a positive rRT-PCR result on any specimen will confirm a Zika virus infection. Usually, no additional testing is required. However, a negative rRT-PCR result does not exclude the Zika virus infection; therefore, the serum should then be analyzed by a serological test for the Zika virus IgM antibody.
