Martha L Ospina, et al.

Background: In 2015 and 2016, Colombia had a widespread outbreak of Zika virus.Data from two national population-based surveillance systems for symptomatic Zika virus disease (ZVD) and birth defects provided complementary information on the effect of the Zika virus outbreak on pregnancies and infant outcomes.

Methods: We collected national surveillance data regarding cases of pregnant women with ZVD that were reported during the period from June 2015 through July 2016.The presence of Zika virus RNA was identified in a subgroup of these women on real-time reverse-transcriptase-polymerase-chain-reaction (rRT-PCR) assay.Brain or eye defects in infants and fetuses and other adverse pregnancy outcomes were identified among the women who had laboratory-confirmed ZVD and for whom data were available regarding pregnancy outcomes.We compared the nationwide prevalence of brain and eye defects during the outbreak with the prevalence both before and after the outbreak period.

Results: Of 18,117 pregnant women with ZVD, the presence of Zika virus was confirmed in 5926 (33%) on rRT-PCR.Of the 5673 pregnancies with laboratory-confirmed ZVD for which outcomes had been reported, 93 infants or fetuses (2%) had brain or eye defects.The incidence of brain or eye defects was higher among pregnancies in which the mother had an onset of ZVD symptoms in the first trimester than in those with an onset during the second or third trimester (3% vs.1%).A total of 172 of 5673 pregnancies (3%) resulted in pregnancy loss; after the exclusion of pregnancies affected by birth defects, 409 of 5426(8%) resulted in preterm birth and 333 of 5426 (6%) in low birth weight.The prevalence of brain or eye defects during the outbreak was 13 per 10,000 live births, as compared with a prevalence of 8 per 10,000 live births before the outbreak and 11 per 10,000 live births after the outbreak.

Conclusions: In pregnant women with laboratory-confirmed ZVD, brain or eye defects in infants or fetuses were more common during the Zika virus outbreak than during the periods immediately before and after the outbreak.The frequency of such defects was increased among women with a symptom onset early in pregnancy.