Which congenital malformations are associated with Zika virus infection?

Updated: Jun 30, 2021
  • Author: Bhagyashri D Navalkele, MD, MBBS; Chief Editor: Michael Stuart Bronze, MD  more...
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Although Zika virus infection is generally well-tolerated, great concern is emerging over congenital malformations due to transplacental transmission of Zika virus. Six months after an outbreak of Zika virus infection began in Brazil, the incidence of microcephaly increased twenty-fold. Whereas the historical prevalence of microcephaly was 2 cases per 10,000 live births, 1248 new suspected cases of microcephaly were reported in 2015, [14, 15] and, as of January 2016, the number of suspected microcephaly cases increased to 4810, of which 270 were confirmed and 462 rejected as false diagnoses of microcephaly. [15]

Infants born with congenital microcephaly and suspected vertical acquisition of Zika virus have been found to have various ophthalmologic abnormalities, including loss of foveal reflex, macular pigment mottling, chorioretinal macular atrophy, optic nerve head hypoplasia, and optic nerve double-ring sign. [14]

Of note, causality has not been definitively proven, and concerns exist over the accuracy of the historical incidence of microcephaly and potential increased diagnoses in the past year leading to a false perception of increased incidence. [15]

A study of 35 infants with microcephaly (defined as head circumference ≥2 standard deviations below the mean for sex and gestational age) born between August and October 2015 in various states throughout Brazil found that the mothers of all 35 had lived in or visited Zika virus–affected areas during pregnancy. [16] Twenty-seven of these infants had severe microcephaly, and test results were negative for other congenital infections in all cases. Zika virus RNA has also been detected in amniotic fluid and placental and fetal tissue in several cases of nervous-system malformations amid the current Brazilian outbreak. [15]

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