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Updated CDC Guidance Expands PCR-Based Zika Testing for Pregnant Women

NEW YORK (GenomeWeb) – The US Centers for Disease Control and Prevention today issued updated interim guidelines concerning testing of pregnant women with possible exposure to the Zika virus. The guidelines now recommend that serum and urine from all pregnant women with Zika symptoms be tested using RT-qPCR assays up to two weeks after symptom onset.

As of July 14, 400 pregnant women in the 50 US states and the District of Columbia and 378 pregnant women in all US territories have received laboratory evidence of confirmed or possible Zika infection — which can be transmitted to fetuses and is thought to cause microcephaly in some cases.

The new guidelines are now an attempt to increase the proportion of definitive diagnoses for pregnant women with Zika infections, which can potentially impact prenatal management. The CDC had previously updated its guidance for symptomatic people to include PCR-based urine testing up to two weeks after possible exposures versus a window of one week after symptom onset for serum testing.

The new recommendation for pregnant women extends the window for testing of serum by one week, a modification prompted by the agency's new evidence of prolonged detection of Zika virus RNA in pregnant women, as it reported in the journal Obstetrics and Gynecology.

Additionally, pregnant women who do not live in areas with active Zika transmission and who do not have symptoms of Zika infection, but who may have been exposed — by travel or by sexual contact — should be tested using RT-qPCR of serum and urine for up to two weeks after the possible exposure, the agency suggested.  

For two to 12 weeks after either symptoms or possible exposure for pregnant women, the agency recommended Zika virus and dengue virus immunoassays followed by reflex RT-qPCR of serum and urine for positive or equivocal Zika results and all dengue results. Furthermore, it suggested a plaque reduction neutralization test as a final assay in certain conditions.

Among PCR-based tests granted Emergency Use Authorization by the US Food and Drug Administration, the CDC's Trioplex assay, Altona's RealStar Zika Virus RT-PCR kit, and a test from Eurofins subsidiary Viracor-IBT Laboratories are authorized for detection of Zika virus in urine. Two tests from Hologic have been authorized for serum and plasma and a Quest Diagnostics test has been authorized for serum samples.

The CDC also issued updated guidance today for prevention of sexual transmission of Zika virus, with recommendations now taking into account the potential for female-to-male transmission. As of July 20, there have been 15 cases of sexually-transmitted Zika reported in the US, the agency noted, and in one case in France, RT-qPCR was able to detect Zika virus RNA in semen 93 days after infection.