Note: For purposes of interpretation, a non-negative Zika virus IgM serology test result may include positive, equivocal, presumptive positive, or possible positive.
- Symptomatic non-pregnant individuals with possible Zika virus exposure should be tested for the Zika virus as follows:
For specimens collected <14 days post-symptom onset, a Zika NAT test should be performed (such as an rRT-PCR test). If positive for NAT, the individual is considered to have an acute Zika virus infection. If negative for Zika NAT, the specimen should be further tested for Zika virus IgM serology.
For specimens collected ≥14 days post-symptom onset, no NAT is performed, but the specimen is tested directly for Zika IgM serology.
A negative test for Zika IgM indicates that the individual is considered to have no evidence of Zika virus infection. If non-negative for Zika virus IgM, then a PRNT test should be performed.
A PRNT Zika virus test ≥10 and a Dengue Virus PRNT <10 indicate a Zika virus infection, but the timing of infection cannot be determined.
A PRNT Zika virus test ≥10 and Dengue Virus PRNT ≥10 indicate a Flavivirus infection, but the timing of infection cannot be determined.
A PRNT Zika virus test of <10 indicates no evidence of Zika virus infection.
Note: See the accompanying algorithm for more details.
- Symptomatic pregnant women with possible Zika virus exposure should be tested in the following manner:
Testing should be done as soon as possible through 12 weeks after symptom onset. The specimen should be tested by both NAT (serum and urine) and Zika virus IgM serology (serum).
If Zika virus NAT is positive, the individual is considered to have acute Zika virus infection.
If negative for Zika virus NAT and negative for Zika virus IgM serology, then the individual is considered to not have evidence of Zika virus infection.
If negative for Zika virus NAT and non-negative for IgM serology, the specimen should be tested by PRNT. If the Zika virus PRNT is <10, then the individual is considered to not have evidence of Zika virus infection.
If Zika virus PRNT is ≥10 and Dengue virus PRNT is <10, then the individual is considered to have a Zika virus infection, but the timing of infection cannot be determined.
If Zika virus PRNT is ≥10 and Dengue virus PRNT is ≥10, then a flavivirus infection is considered, and the specific virus and timing of infection cannot be determined.
NOTE: See the accompanying algorithm for more details.
