Abstract
BackgroundZika virus caused thousands of congenital anomalies during a recent epidemic. Because Zika emerged in areas endemic for dengue and these related flaviviruses elicit cross-reactive antibodies, it is challenging to serologically monitor pregnant women for Zika infection.MethodsA prospective cohort of 253 pregnant women was established in León, Nicaragua. Women were followed during prenatal care through delivery. Serologic specimens were obtained at each visit, and birth outcome was recorded. Established flavivirus serologic methods were adapted to determine Zika seroprevalence, and a stepwise testing algorithm estimated timing of Zika infection in relation to pregnancy.ResultsZika seroprevalence was approximately 59% among women tested. Neutralization testing was highly concordant with Zika NS1 BOB results. Per study algorithm, 21% (40/187) of women were classified as experiencing Incident ZIKV infection during pregnancy. Importantly, the Incident ZIKV group included mostly women pregnant during the 2016 Zika epidemic peak and the only 3 subjects in the cohort with RT-PCR-confirmed infections. Approximately 17% of births had complications; 1.5% (3/194) manifesting clinical criteria of congenital Zika syndrome, one was RT-PCR-confirmed as a case of congenital Zika syndrome. Adverse birth outcome did not correlate with timing of Zika infection.ConclusionsBy leveraging prenatal care systems, we developed a simple algorithm for identifying women who were likely infected by Zika during pregnancy.
Highlights
Zika virus (ZIKV) spread rapidly throughout Latin America and the Caribbean in 2015–2016. [1] ZIKV is an enveloped, positive-sense RNA virus primarily transmitted by Aedes aegypti, which is the vector of dengue (DENV), yellow fever, and chikungunya viruses
Neutralization testing was highly concordant with Zika Nonstructural protein 1 (NS1) blockade of binding (BOB) results
21% (40/187) of women were classified as experiencing Incident ZIKV infection during pregnancy
Summary
Zika virus (ZIKV) spread rapidly throughout Latin America and the Caribbean in 2015–2016. [1] ZIKV is an enveloped, positive-sense RNA virus primarily transmitted by Aedes aegypti, which is the vector of dengue (DENV), yellow fever, and chikungunya viruses. ZIKV has primarily circulated in DENV-endemic areas. ZIKV can be transmitted from pregnant mother to fetus, causing fetal loss, growth restriction, and congenital Zika syndrome (CZS), which consists of a constellation of findings including microcephaly, fetal brain and ocular anomalies, and contractures [5,6,7]. Because diagnosis of acute symptomatic ZIKV infection is difficult, only a small proportion of cases (~5%) were confirmed by laboratory testing many months into the epidemic.[8] The inability to accurately diagnose ZIKV infection severely hampered efforts to track ZIKV infection within the general population, develop interventions to control the spread of the virus, and clinically manage infected individuals including pregnant women living in endemic areas. Because Zika emerged in areas endemic for dengue and these related flaviviruses elicit cross-reactive antibodies, it is challenging to serologically monitor pregnant women for Zika infection
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