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    Zika: A report from the front lines


    iii. If >12 weeks, obtain a Zika IgM and begin serial fetal ultrasounds. If the IgM is positive or equivocal, or there are characteristic fetal abnormalities present on ultrasound, order rRT-PCR on serum and urine (also consider amniocentesis for amniotic fluid rRT-PCR testing if the ultrasound is abnormal). Note, false-negative IgM and rRT-PCR results are possible >12 weeks after exposure or symptom onset since IgM and viral RNA levels decline over time. Given the limitations of testing beyond 12 weeks after symptom onset or latest possible exposure history, serial fetal ultrasounds should be considered in such cases.


    B. Exposed Asymptomatic Patients:

    Our approach at the University of South Florida is to estimate time from last exposure and: 

    i.  If <2 weeks, order serum and urine rRT-PCR testing for Zika RNA. A positive result confirms infection. A negative result should prompt ordering IgM for Zika at 2 to 12 weeks with PRNT studies if positive or equivocal.

    ii.  If 2 to 12 weeks, order IgM for Zika. If positive or equivocal, order reflex rRT-PCR testing of the same serum sample, and I would add urine testing as well. Again the presence of viral RNA confirms the diagnosis. If the rRT-PCR is negative, PRNT should be performed and again a positive Zika and negative dengue PRNT should also be considered diagnostic of infection as noted above.

    iii.  If >12 weeks obtain Zika IgM and serial fetal ultrasound as described above.


    2. For ob/gyns practicing in areas with documented local mosquito-borne Zika transmission or when patients frequently travel to such areas:

    A.  Query patients about possible Zika-related signs and symptoms and if positive immediately initiate testing as outlined under the guidance for symptomatic patients listed above.

    B. Initiate screening in asymptomatic patients:

    i. At first visit, order IgM for Zika, and if results are positive or equivocal, order reflex rRT-PCR of serum. I would again suggest testing a urine sample to maximize sensitivity. A positive rRT-PCR result is diagnostic of infection. If the rRT-PCR study is negative, order PRNT analyses and assess as described above. If the initial Zika IgM is negative, repeat at 16 to 24 weeks.

    ii.  I would recommend “screening” ultrasounds at 18 and 22 weeks where resources are available. Characteristic Zika-related ultrasound abnormalities should prompt rRT-PCR and serologic testing.

    All confirmed Zika infections should be followed by serial ultrasounds. Current CDC recommendations call for scans every 3 to 4 weeks, however, I would recommend obtaining these every 2 weeks starting 6 weeks after the presumed date of infection and ideally by 18 weeks’ gestation. The presence of characteristic CNS abnormalities in a patient with a confirmed infection is diagnostic of congenital Zika infection and patients should be counseled accordingly. For those not opting for pregnancy termination either by choice or because of advanced gestational age, fetal testing may be indicated given the risk of hydrops, fetal growth restriction, and fetal loss. However, such decisions should be made after a full discussion of fetal prognosis with the parents.

    Some have questioned the utility of serologic and rRT-PCR testing in exposed patients, suggesting that serial ultrasounds should detect major abnormalities. I disagree. Confirmation of an actual infection should prompt more frequent and more targeted sonographic assessments. Another concern of ob/gyns in areas of active transmission, is the potential for subtle or severe long term neurodevelopmental sequelae in children who did not display overt fetal CNS abnormalities on prenatal ultrasound.2 

    While there is no current evidence to support such a thesis, some patients with serologically confirmed infections, particularly those occurring earlier in pregnancy, may opt for termination to mitigate such risks or if diagnosed near mid-gestation may elect termination for fear that fetal CNS abnormalities may present after the legal limit of termination. Clearly such “unknowns” present complex challenges to counseling affected patients.

    Information was up to date at time of publication.  For the latest Zika news visit ContemporaryOBGYN.net/Zika-updates


    Charles J. Lockwood, MD, MHCM
    Dr. Lockwood, Editor-in-Chief, is Dean of the Morsani College of Medicine and Senior Vice President of USF Health, University of South ...


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