Microcephaly Epidemic in Brazil: An Earlier Chapter

Background: The first cases of Zika virus infection and microcephaly in Brazil were reported in 2015. However, phylogenetic studies suggest that the virus may have previously circulated in the country. Methods: The head circumference of 62,298 newborns was analysed to identify cases of microcephaly between 2014 and 2017. We compared the groups of newborns with normal head circumference and those with microcephaly to identify risk factors. A time series with the incidences of microcephaly was analysed to assess the appearance of anomalous values to identify the beginning of the microcephaly epidemic. Data on the incidence of dengue fever were used to develop a control chart, aiming to identify changes in incidence and seasonality that could suggest the circulation of a new arbovirus. Findings: Premature newborns, children of mothers under 20 years of age and those born in 2014 and 2015 had a higher risk of microcephaly. Three quarters with anomalous incidences of microcephaly were identified, the first in 2014 and the others in 2015. The dengue epidemic curve in 2013 shows persistence of high incidences in atypical periods, suggesting the entry of a new virus in the third and fourth quarters. Interpretation: These findings represent epidemiological evidence of the existence of cases of Zika virus between the second quarter of 2013 and the beginning of 2014. The results add new elements to understanding the Zika virus epidemic in the Americas. Funding Statement: No funding was received. Declaration of Interest: Declaration of interests: We declare no competing interests Ethical Approval Statement: The ethics and research committee of the Federal University of Paraiba (2.520.770, CAAE 81168517.6.0000.8069) approved the research.