, including those who may have been exposed before pregnancy through travel or sexual contact.
In updated guidance released July 24, the Centers for Disease Control and Prevention cited a combination of factors behind the change in recommendations, including the declining prevalence of Zika virus across the Americas and a high likelihood of false positives associated with the use of a common serologic assay (MMWR Morb Mortal Wkly Rep. ePub 2017 Jul 24.).
Positive IgM results can also occur after previous exposure to other flaviviruses besides Zika, Dr. Oduyebo and her colleagues noted.
The CDC now recommends that pregnant women with likely continuing – not previous – exposure to the Zika virus and those with symptoms suggestive of Zika virus disease be tested. Those higher-risk groups should receive nucleic acid testing (NAT).
The new guidance presents two updated testing algorithms, one for each group.
Any pregnant woman with symptoms suggestive of Zika should be tested “as soon as possible through 12 weeks after symptom onset,” the CDC said, with both NAT (serum and urine) and IgM serology testing.
Women with likely ongoing exposure to Zika – such as those living in or traveling to an area of mosquito-borne Zika transmission or those whose partners are living in or traveling to such an area – should be tested up to three times during the pregnancy using NAT serum and urine tests. IgM testing is not recommended for that group.
All pregnant women should be asked about their potential Zika exposures before and during the current pregnancy, the CDC said. That discussion, which covers potential travel and partner exposures along with questions about symptoms, should be repeated at every prenatal visit.
While routine testing of asymptomatic women without ongoing exposure is not recommended, patient preferences, clinical judgment, and a “balanced assessment of risks and expected outcomes” should guide decisions about testing, according to the CDC.