Spatio-temporal modeling of congenital syphilis: a 15-year ecological and population-based study

Congenital syphilis remains a critical public health concern in Brazil, contributing significantly to neonatal mortality and morbidity. This study analyzes the epidemiologic profile, temporal trend and spatio-temporal dynamics of reported congenital syphilis cases in Brazil from 2010 to 2024. We conducted an ecological study using secondary data extracted from the Brazilian National Notifiable Diseases Information System (SINAN, acronym in Portuguese). Clinical and sociodemographic variables as well as epidemiologic indicators were analyzed. The temporal trend was assessed using Joinpoint Regression analysis and the space–time clusters were identified through scan statistics. A 5% significance level and 95% confidence intervals were applied throughout the analysis. From 2010 to 2024, 282,919 cases of congenital syphilis were reported. Most mothers were aged < 30 years (76.2%), were black (56.5%) and had low educational attainment (38.2%). Although 81.1% of the mothers underwent prenatal care, only 17.7% of the sexual partners were treated. Most cases (95.9%) were categorized as early congenital syphilis. The national incidence rate rose from 2.35/1.000 live births in 2010 to 4.65/1.000 live births in 2024 (Annual Average Percent Change: 5.6%; p < 0.001) and all regions presented increasing tendencies, with the steepest increases in the Center-west (AAPC: 9.9%; p < 0.001) and North (AAPC: 8.3%; p < 0.001) regions. Goiânia and Belém showed the highest trends among the capitals (+ 27% e + 20.1% per year, respectively). Scan statistics identified 35 clusters in the purely spatial analysis, with the highest relative risks observed in regions of Rio de Janeiro (RR 3.1 and 3.0) and Rio Grande do Sul (RR 3.4). In the retrospective space–time analysis, 13 clusters were detected, with the highest relative risks found in Rio Grande do Sul and São Paulo (both with RR 2.8). The prospective space–time analysis revealed 4 clusters, with the highest relative risk (RR 3.2) located in a cluster spanning areas of Rio de Janeiro and Minas Gerais. Congenital syphilis incidence in Brazil increased markedly, with a heterogenous spatial distribution. The results point to fragilities in prenatal care, particularly regarding partner treatment coverage, and gaps in epidemiologic surveillance.