Elsevier

Epidemics

Volume 15, June 2016, Pages 66-70
Epidemics

A theoretical estimate of the risk of microcephaly during pregnancy with Zika virus infection

https://doi.org/10.1016/j.epidem.2016.03.001Get rights and content
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Highlights

  • The notification of microcephaly associated with a large Zika virus epidemic was observed in Brazil, 2015.

  • Accounting for the time interval from infection in pregnancy to microcephaly, the risk of microcephaly was estimated.

  • The risk of microcephaly in Northeastern Brazil was estimated at 14.0% or greater.

Abstract

Objectives

There has been a growing concern over Zika virus (ZIKV) infection, particularly since a probable link between ZIKV infection during pregnancy and microcephaly in the baby was identified. The present study aimed to estimate a theoretical risk of microcephaly during pregnancy with ZIKV infection in Northeastern Brazil in 2015.

Methods

Temporal distributions of microcephaly, reported dengue-like illness and dengue seropositive in Brazil were extracted from secondary data sources. Using an integral equation model and a backcalculation technique, we estimated the risk of microcephaly during pregnancy with Zika virus infection.

Results

If the fraction of Zika virus infections among a total of seronegative dengue-like illness cases is 30%, the risk of microcephaly following infection during the first trimester was estimated at 46.7% (95% CI: 9.1, 84.2), comparable to the risk of congenital rubella syndrome. However, the risk of microcephaly was shown to vary widely from 14.0% to 100%. The mean gestational age at delivery with microcephaly was estimated at 37.5 weeks (95% CI: 36.9, 39.3).

Conclusions

The time interval between peaks of reported dengue-like illness and microcephaly was consistent with cause–outcome relationship. Our modeling framework predicts that the incidence of microcephaly is expected to steadily decline in early 2016, Brazil.

Keywords

Microcephaly
Zika infection
Gestation
Statistical estimation
Brazil

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