Ongoing Outbreak of Neisseria meningitidis Serogroup B in Pará State, Brazilian Amazon Region, Following the COVID-19 Pandemic

Abstract

Abstract Background Invasive meningococcal disease (IMD) remains a major cause of mortality worldwide, yet its dynamics in the Brazilian Amazon are poorly understood. Following the COVID-19 pandemic, serogroup B IMD resurged in Brazil, raising concerns about changing transmission patterns in regions with limited healthcare access. Methods We conducted an epidemiological and genomic investigation of an ongoing IMD outbreak in Pará State, Brazilian Amazon, between 2023 and 2025. Clinical, demographic, and outcome data were integrated with whole-genome sequencing of 69 isolates. Multivariate logistic regression identified independent predictors of mortality, and phylogenomic analyses characterized transmission dynamics and clonal expansion. Results A total of 343 IMD cases were identified, of which 321 (93.6%) were caused by serogroup B, resulting 34 deaths (case-fatality rate, 10.6%). Incidence increased up to 5-fold compared with national rates and disproportionately affected young children and adults. Mortality was independently associated with meningococcemia (adjusted odds ratio, 84.52; 95% confidence interval, 5.70–1253.65; P = .001); however, this finding should be interpreted with caution due to the small number of meningococcemia cases. Genomic analysis identified a predominant ST-7983/cc60 lineage, accounting for 64 of 69 sequenced isolates (92.7%). This lineage displayed limited genetic diversity (median, 7 single nucleotide polymorphisms), consistent with sustained regional transmission across multiple municipalities. Conclusions A highly clonal serogroup B meningococcal outbreak emerged in the Brazilian Amazon following the COVID-19 pandemic, with substantial mortality and rapid geographic spread. These findings highlight the importance of strengthened genomic surveillance and support targeted vaccination strategies to improve outbreak preparedness in underserved regions.