Geographical and temporal variations of serogroups and clonal types of involved in culture-confirmed invasive meningococcal disease in Canada, 2015-2023.

Invasive meningococcal disease (IMD) is a nationally notifiable illness in Canada due to its potential severity and transmissibility. Vaccination strategies differ by province/territory and are informed by changes in the antigenic characteristics of circulating strains. Though IMD statistics are tracked at a provincial/territorial level, there is a lack of published data characterizing trends in the epidemiology of this disease at a national level. To examine the epidemiology of culture-confirmed IMD in Canada during the period of 2015-2023. Meningococcal isolates sent to the National Microbiology Laboratory Branch between 2015 and 2023 as part of routine national surveillance were characterized for serogroup by bacterial agglutination and genetic methods. Clonal analysis was done by MLST. Demographic information was derived from requisition forms accompanying the samples. The proportion of IMD caused by serogroup W meningococci (MenW) in 2015-2023 was 30.0% with more (62.9%) MenW cases detected in western provinces. Serogroup B meningococci (MenB) IMD was more common (53.4%) in Quebec and Atlantic Canada. Clonal analysis reveals 168 distinct sequence types between 2015 and 2023, with 103 belonging to MenB. The average age of MenB cases during this time was 29.1 years, significantly younger than serogroup C (MenC) (45.3 years), serogroup Y (MenY) (48.3 years) and MenW (43.0 years) patients. Additionally, 31.5% of MenB and 21.7% of MenC IMD isolates were collected from cerebrospinal fluid (CSF) or brain samples, which were significantly higher than that for MenY (12.2%) and MenW (7.3%) isolates. Results from this and previous studies showed temporal and geographical variations in the serogroups causing IMD in Canada. MenB also showed the most genetic diversity, caused IMD in a significantly younger population and was more often isolated from CSF and brain samples than other serogroups.