From Epidemic to Endemic: Longitudinal Surveillance of Congenital Zika Syndrome in Brazil
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Zika virus (ZIKV) emerged in Brazil in 2015, causing an unprecedented epidemic of Congenital Zika Syndrome (CZS). A decade later, longitudinal analyses evaluating temporal trends and subnational heterogeneity in CZS burden remain limited. Using publicly available data from SINAN/DATASUS and the RESP-Microcephaly registry (SVS/Ministry of Health, updated July 2024), we conducted a descriptive ecological analysis of ZIKV infection and CZS in Brazil from 2015 to 2023. Of 331,309 notified Zika cases (2015-2023), 213,350 occurred in 2016, followed by an 91.75% decline in 2017 and sustained low-level endemic circulation thereafter. Among 3,751 confirmed microcephaly cases, 1,828 were confirmed with ZIKV etiology. The Northeast region accounted for 75.4% of confirmed cases despite representing approximately 27% of the national population. State-level analyses revealed distinct epidemiological patterns, including persistent microcephaly notifications of non-Zika etiology in Minas Gerais and continued detection of ZIKV-attributed CZS in Amazonas and Goiás through 2023. These findings highlight pronounced geographic disparities in congenital Zika burden, reflect significant heterogeneity in diagnostic capacity, and underscore the need for sustained surveillance and systematic etiological investigation of congenital abnormalities in the post-epidemic era.
AUTHOR SUMMARY
When Zika virus spread across Brazil in 2015, a wave of babies was born with abnormally small heads and severe brain damage, a condition now known as Congenital Zika Syndrome. The epidemic shocked the world, but by 2017 case numbers had dropped sharply, leading many to ask: has this syndrome disappeared? In this study, we analyzed eight years of Brazilian public health data (2015–2023) to track Zika infections and cases of congenital brain abnormalities over time and across all Brazilian states. Our findings reveal that, while the dramatic epidemic peak has passed, Zika virus continues to circulate at low levels and babies continue to be born with Zika-related brain damage each year. We also uncovered striking geographic inequalities: the Northeast region, home to about 27% of Brazil’s population, accounted for over 75% of confirmed cases. States with higher poverty and poorer sanitation were hardest hit. We found that the ability to correctly identify the cause of brain abnormalities varied widely across states, raising concerns that some cases may go undetected. Our results highlight that Congenital Zika Syndrome has not disappeared, it has simply become less visible. Sustained monitoring and investigation of congenital brain abnormalities remain essential public health priorities.
