High-risk clusters and temporal trends in congenital syphilis infection in Brazil

Objective. To determine the occurrence of high-risk clusters for congenital syphilis (CS) in Brazil and describe the temporal trends in the CS infection in the country, comparing children whose mothers received vs. those whose mothers did not receive prenatal care. Method. This ecological study used data from the National Disease Notification System (Sistema de Informacao de Agravos de Notificacao, SINAN) and the Live Birth Information System (Sistema de Informacoes sobre Nascidos Vivos, SINASC). For cluster analysis, the Kulldorff scan statistic was applied to the population at risk. Statistical significance was determined by the log-likelihood ratio based on Poisson discrete distribution. To analyze the temporal trends of disease detection rates, Prais-Winsten regression was used. The analysis was performed with SatScan 9.4 and Stata 14.0 software. Results. Clusters with detection rates of 41.3, 44.4 and 188.1 CS cases/10 000 live births were identified in 2001, 2009 and 2017 respectively. In 2001, the rates were 8 times higher in the clusters than in the remaining country; in 2009, the rates were 3.3 times higher; and in 2017, 2.5 times higher. An increasing trend in CS infection was detected in all regions and federation units. The rates were 8.53 times higher in the children of mothers without prenatal care (243.3 cases/1 000 live births vs. 28.3 cases/1 000 live births in the children of mothers with prenatal care). Conclusions. The identification of municipality clusters at high risk for CS and of increasing trends in CS infection across the country, even in the presence of prenatal care, suggests the need for improvement of public health actions to fight this disease.