We have previously blogged about Zika virus   during pregnancy.That post was in February of 2016 and a lot has changed since then.

For one thing, Zika has been shown to be transmitted via sexual contact from an infected individual (even if he or she does not have symptoms) to a non-infected individual.  The use of condoms can help, and there are guidelines for the pre-conception prevention of sexual transmission.

In addition, scientists at the CDC have concluded that Zika virus infection does cause microcephaly and other brain defects. This means that women who are infected with Zika virus during pregnancy are at increased risk of having a baby with these problems, but it does not mean that all women with Zika virus infection during pregnancy will have these problems.

Other changes that have occurred since last year include the FDA’s Emergency Use Authorization (EUA) for several diagnostic tools for Zika virus, including the Trioplex Real-Time RT-PCR (rRT-PCR) assay and the Zika MAC-ELISA.

The Trioplex assay is for the detection of RNA from dengue, chikungunya and Zika viruses in serum, whole blood (EDTA), and cerebrospinal fluid (CSF). This is important since dengue and chikungunya are often in the same differential diagnosis with Zika virus. The assay can also be used to detect Zika virus RNA in urine & amniotic fluid.

The Zika MAC-ELISA is intended for the qualitative detection of Zika virus IgM antibodies in human sera or cerebrospinal fluid (CSF).  however, due to cross-reaction with other flaviviruses and possible nonspecific reactivity, results may be difficult to interpret. Consequently, presumed positive, equivocal, or inconclusive tests must be confirmed by plaque-reduction neutralization testing (PRNT).

According to the CDC, who should be tested?

Asymptomatic Pregnant Women

For asymptomatic pregnant women who have traveled to areas with active Zika virus transmission, RNA nucleic acid testing (NAT) testing is recommended on serum and urine within 2 weeks of the date of last possible exposure. Zika virus-specific IgM testing should be performed on women within 2-12 weeks after travel to an area of active transmission or who have had sexual contact with a man confirmed to have Zika virus infection. In areas with active Zika virus transmission, asymptomatic pregnant women should undergo IgM testing as part of routine obstetric care in the 1st and 2nd trimesters. Presumed positive, equivocal, or inconclusive IgM results must be confirmed by plaque reduction neutralization test (PRNT).

Symptomatic Pregnant Women

For symptomatic pregnant women with exposure to Zika virus, RNA nucleic acid testing (NAT) of serum and urine is recommended up to 2 weeks after symptom onset. Whole blood can also be tested for Zika RNA alongside serum and urine. Urine should always be collected with a patient-matched serum specimen. A positive RNA NAT result on any sample confirms Zika virus infection and no additional testing is indicated. A negative RNA NAT result does not exclude Zika virus infection and serum should be tested for the presence of IgM antibodies. If more than 2 weeks have passed since the onset of Zika virus symptoms, specific IgM testing is recommended. Reflex RNA NAT testing should be performed as a subsequent test for pregnant women who are IgM positive.

For recommendations of testing non-pregnant women, and infants, visit the FDA website.

Originally published by The Pregnancy Lab

About The Author

Professor of Pathology & Immunology, and Obstetrics & Gynecology, Washington University School of Medicine

Dr. Gronowski is a Professor of Pathology & Immunology, and Obstetrics & Gynecology at Washington University School of Medicine (St. Louis Missouri). She is Associate Medical Director of the Clinical Chemistry and Serology & Immunology laboratories at Barnes-Jewish Hospital. Dr. Gronowski received her Ph.D. in Endocrinology- Reproductive Physiology from University of Wisconsin, and is a diplomate of the American Board of Clinical Chemistry. Dr. Gronowski is past president of the American Board of Clinical Chemistry and the American Association for Clinical Chemistry. Her research focuses primarily on the laboratory diagnostics of endocrinology and reproductive physiology with a particular emphasis on maternal fetal medicine. She edited the book entitled “Handbook of Clinical Laboratory Testing During Pregnancy”.