Background
Cerebrospinal meningitis (CSM) remains a significant public health challenge in Nigeria and the African meningitis belt, which bears the highest global burden of meningococcal disease. Although vaccination has largely controlled Neisseria meningitidis serogroup A, emerging serogroups, particularly serogroup C (NmC), continue to drive outbreaks in West Africa. Unlike the low‑incidence, sporadic patterns seen in Europe and the United States, the region experiences seasonal epidemics with high case‑fatality ratios and limited laboratory confirmation. Understanding Nigeria’s evolving epidemiology is therefore critical for regional preparedness and global meningococcal control efforts.
Methods
We conducted the first post‑COVID national longitudinal analysis of CSM surveillance data from Nigeria’s IDSR system, covering October 2020–March 2026. Analyses included age, sex, seasonality, and pathogen serogroup. Laboratory confirmation and serogrouping were performed using PCR, and descriptive statistics and epidemic curves were generated in R.
Results
Of 799 PCR-confirmed cases, Neisseria meningitidis serogroup C (NmC) predominated (79.1%), followed by serogroup W (12.8%), Streptococcus pneumoniae (3.5%), Haemophilus influenzae (3.0%), and serogroup X (1.2%). Males comprised 65.2% of cases. Children aged 5–14 years were mostly affected (53.5%), followed by those aged 15–29 years (24.0%). NmC infections primarily affected older children and adolescents, while non-NmC pathogens were more common among children aged <5 years. Between the 2020/2021 and 2025/2026 seasons, 14,546 suspected CSM cases, 799 laboratory-confirmed cases, and 772 deaths were reported. Suspected cases increased from 496 in 2020/2021 to a peak of 4,915 in 2023/2024, remained high in 2024/2025 (4,829), and declined to 847 cases in 2025/2026 to date. Case fatality ratios, (CFRs) ranged from 3.0% to 13.9%, reaching 10.9% in 2025/2026.
Conclusion
CSM remains endemic in Nigeria, with persistent NmC dominance and recurrent outbreaks. The post-COVID resurgence and sustained high CFRs highlight the need to strengthen surveillance, PCR diagnostic capacity, timely clinical management, and multivalent meningococcal vaccination strategies.