The association between Zika virus infection and microcephaly in Brazil 2015 –2017: An observational analysis of over 4 million births

by Oliver J. Brady, Aaron Osgood-Zimmerman, Nicholas J. Kassebaum, Sarah E. Ray, Valdelaine E. M. de Ara újo, Aglaêr A. da Nóbrega, Livia C. V. Frutuoso, Roberto C. R. Lecca, Antony Stevens, Bruno Zoca de Oliveira, José M. de Lima Jr., Isaac I. Bogoch, Philippe Mayaud, Thomas Jaenisch, Ali H. Mokdad, Christopher J. L. Murray, Simon I. Hay, Robert C. Reiner Jr., Fatima Marinho BackgroundIn 2015, high rates of microcephaly were reported in Northeast Brazil following the first South American Zika virus (ZIKV) outbreak. Reported microcephaly rates in other Zika-affected areas were significantly lower, suggesting alternate causes or the involvement of arboviral cofactors in exacerbating microcephaly rates. Methods and findingsWe merged data from multiple national reporting databases in Brazil to estimate exposure to 9 known or hypothesized causes of microcephaly for every pregnancy nationwide since the beginning of the ZIKV outbreak; this generated between 3.6 and 5.4 million cases (depending on analysis) over the time period 1 January 2015 –23 May 2017. The association between ZIKV and microcephaly was statistically tested against models with alternative causes or with effect modifiers. We found no evidence for alternative non-ZIKV causes of the 2015–2017 microcephaly outbreak, nor that concurrent exposure to arbovirus infection o r vaccination modified risk. We estimate an absolute risk of microcephaly of 40.8 (95% CI 34.2–49.3) per 10,000 births and a relative risk of...
Source: PLoS Medicine - Category: Internal Medicine Authors: Source Type: research