Further evidence that Zika virus disease associated with brain and eye birth defects

1. The prevalence of brain and eye defects was elevated during the 2015-2016 Zika virus outbreak in Colombia compared to the periods immediately before and after the outbreak.

2. Pregnant women who began displaying symptoms of Zika virus disease in the first trimester were significantly more likely to have a preterm birth or pregnancy loss compared to those who had later symptom onset.

Evidence Rating Level: 2 (Good)

Study Rundown: In 2015, an outbreak of the Zika virus began in Brazil and quickly swept through the Americas. Colombia was among the countries most affected by the epidemic, with more than 100,000 individuals displaying symptoms of Zika virus disease (ZVD) in less than one year’s time. Further, a study conducted in 2016 revealed that the frequency of microcephaly in the nation had quadrupled since the previous year, consistent with other studies that suggested an association between antenatal exposure to Zika virus and various neurodevelopmental abnormalities. Given the relatively mild severity of the disease in the overall population, it was likely that a significant number of cases went unreported; thus, the extent to which this increase in birth defects could be attributed to ZVD was unclear. In this study, national birth defect surveillance data and ZVD surveillance data were analyzed in order to evaluate the occurrence of brain and eye defects in several groups and subgroups of pregnant women: those belonging to the general population, those with ZVD symptoms, and those with laboratory-confirmed ZVD. It was found that, among those with laboratory-confirmed ZVD, 2% of their infants had a brain or eye defect; those who had an onset of symptoms during the first trimester were roughly 3 times more likely to have a newborn with a brain or eye defect and roughly 4 times more likely to have pregnancy loss compared to those whose onset occurred in the second or third trimesters. Additionally, the overall prevalence of brain or eye defects was significantly higher in the peri-epidemic period compared to the periods immediately before and after.

Click here to read the study, published in NEJM

Relevant Reading: Zika Virus Infection in Pregnant Women in Rio de Janeiro

In-Depth [retrospective cohort]: Between June 2015 and July 2016, 18,117 pregnant women reported having clinical symptoms of ZVD. Of these women, 5673 had positive serum samples on real-time reverse-transcriptase polymerase chain reaction assays and reported both gestational age at the time of symptom onset and pregnancy outcome. Adverse outcomes were observed in 790 (14%) of these pregnancies, with 93 (2%) being brain or eye defects. The pregnancies of women who had symptom onset in the first trimester accounted for 40 (43%) of these defects despite the subgroup comprising only 1192 individuals (21%). These women were also more likely to have pregnancy loss (8% vs. 2%) or a preterm birth (10% vs. 7%) compared to those with a later symptom onset. Analyzing all pregnancies in Colombia regardless of ZVD status, 1451 infants were born with a brain or eye defect between September 2015 and April 2017. This corresponded to a nationwide prevalence of 13 cases (95% CI, 13-14) per 10,000 live births, with regional prevalences ranging from 5 to 81 per 10,000 live births. In comparison, the overall prevalences in 2014 and 2018 were 8 (95% CI, 7-9) per 10,000 live births and 11 (95% CI, 10-12) per 10,000 live births, respectively.

Image: PD

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