Bettencourt, CéliaNunes, A.VigLab-DM – Network for the Laboratory Surveillance of Meningococcal DiseaseBajanca-Lavado, M.P..2026-02-062026-02-062025-05-26http://hdl.handle.net/10400.18/10841Introduction: Since 2002, laboratory surveillance of Invasive Meningococcal Disease (IMD) has been carried out by the National Reference Laboratory for Neisseria meningitidis, at the National Institute of Health Doutor Ricardo Jorge, Portugal. This study aims to analyse the epidemiology of IMD and the genetic diversity of Neisseria meningitidis strains from 2020 to 2024. Material and Methods: Suspected IMD cases and N. meningitidis isolates were sent to the reference laboratory for confirmation and strain characterization. Invasive isolates were characterized by WGS (Illumina) and sequences were submitted to the PubMLST/Neisseria database. Results: Between 2020 to 2024, 125 IMD cases were confirmed. Annual incidence rate ranged from 0.36 cases/100,000 inhabitants in 2020 to 0.32 in 2023 [1, 2]. Serogroup B was the most prevalent (49.6%), followed by serogroups Y (14.4%), W (13.6%) and C (5.6%). Serogroup W mainly affected those over 45 years old (58.8%). In silico analysis of 89 (71.2%) isolates identified major clonal complexes (cc): B-cc213 (22%) and cc41/44 (18%), Y-cc23 (80%), W-cc11 (66.7%), and C-cc11/cc103 (33.3% each). Conclusions: Compared to previous studies (2003-2020), the incidence of IMD in Portugal has decreased [1-3]. However, serogroup B remains the leading cause of IMD, raising concerns, particularly due to cases in children and emerging clusters with low vaccination coverage (e.g. serogroup B cc213) [4]. In contrast, serogroup W cases have increased, especially among adults [2, 3]. This study highlights the importance of laboratory surveillance for understanding IMD epidemiology and monitoring long-term trends.engSurveillanceInvasive Meningococcal DiseaseDoença invasiva meningocócicaNeisseria MeningitidisPortugalconference object