Maternal Zika virus infection and newborn microcephaly—an analysis of the epidemiological evidence

• Published in: Annals of epidemiology 2018-02, Vol.28 (2), p.111-118
• Main Author: Bautista, Leonelo E.
• Format: Article
• Language: English
• Subjects: Brazil; Disease outbreaks; Microcephaly; Time series analysis; Zika virus
• ISSN: 1047-2797; 1873-2585
• DOI: 10.1016/j.annepidem.2017.11.010

To evaluate whether existing data and evidence support a causal link between maternal Zika virus (ZIKV) infection and newborn microcephaly. I quantified and compared the prevalence of all and severe microcephaly in Brazil, during and before 2015–2016, to assess whether an outbreak has occurred, used time series analysis to evaluate if the presumed outbreak was linked to a previous outbreak of ZIKV infections, and quantitatively synthesized published data from observational studies testing this association. The prevalences of microcephaly in 2015–2016 were similar or lower than background levels (prevalence ratio [PR] for all microcephaly: 0.19; 95% confidence intervals [CI]: 0.17, 0.20). Changes in the number of cases of ZIKV infections at times matching 11–18 weeks of pregnancy were not followed by changes in the number of microcephaly cases (PR for infection at 12 weeks: 1.02; 95% CI: 0.99, 1.05). In observational studies, the prevalence of microcephaly was not significantly increased in newborns of Zika-infected mothers (average PR: 1.30; 95% CI: 0.84, 2.02). Existing evidence is insufficient to claim maternal ZIKV infection causes microcephaly. Although a public health response seems sensible, it should be consistent with existing knowledge and consider risks, potential benefits and harm, and competing priorities.