Living in the Belt: Why Seasonality Dictates the Fight Against Meningitis

Introduction

Cerebrospinal meningitis is a severe disease characterized by inflammation of the protective tissues (meninges) surrounding the brain and spinal cord. It is commonly caused by infectious agents, particularly Neisseria meningitidis.¹ It is a significant public health concern in Sub-Saharan Africa, with the highest burden occurring in the African Meningitis Belt, a region stretching from Senegal to Ethiopia and including Nigeria.¹˒² Meningitis outbreaks in this region show a strong seasonal pattern, with incidence rising to as high as 100 cases per 100,000 population during the dry season.²˒³ Environmental factors such as climate, dust winds, cold nights, and upper respiratory tract infections damage the nasopharyngeal mucosa, increasing vulnerability to meningitis and facilitating transmission.² For Nigerian medical students, understanding the relationship between seasonality and meningitis is crucial, as future clinicians and public health practitioners must be equipped to recognize outbreak patterns, support preventive measures, and respond effectively to epidemics.¹˒³

Environmental Factors Facilitating Meningitis Transmission in the African Belt

The dry season has contributed indirectly to the rise in cases of meningitis seen in the African meningitis belt 4. During this season, certain factors like the harmattan winds, low relative humidity and mineral dust concentrations are at their peak 5. It is associated with the rise in the cases of meningitis and is seen to be gone with the beginning of rainfall 8. The upper respiratory tract (nose, throat, and nasopharynx), which is normally lined by mucus, is the target of the Neisseria meningitidis bacteria 5. They get exposed to the dust and dry air 5. The dry air causes the mucus to lose its moisture, and the increased inhalation of dust can irritate this tract 5,6,9. Dryness and irritation break down the mucosal defenses, allowing for Neisseria Meningitidis to adhere easily to the respiratory tract, multiply and enter the bloodstream to cause meningitis. 5

The Human Dimension of Seasonality: Behavior, Crowding, and Meningitis Transmission

Seasonality shapes meningococcal meningitis not only through environmental conditions but also by infuencing human behavior. During the dry season in the African meningitis belt, cold nighttime temperatures and dusty Harmattan winds encourage people to spend more time indoors, often in overcrowded and poorly ventilated homes, classrooms, and places of worship. These conditions increase close interpersonal contact, facilitating the transmission of Neisseria meningitidis through respiratory droplets. Evidence suggests that while meningococcal carriage may not increase substantially during the dry season, seasonal environmental stress and behavioral factors increase the likelihood that asymptomatic carriage progresses to invasive disease. 10,11

Studies have also shown that household crowding, close sleeping proximity, and exposure to indoor air pollution from cooking fres signifcantly increase the risk of meningococcal carriage and transmission 12. Adolescents and young adults, who typically have the highest social contact rates, play an important role in sustaining subclinical carriage and community transmission. 13 Furthermore, investigations conducted by the MenAfriCar Consortium demonstrated that transmission occurs both within households and through wider community interactions, emphasizing the importance of social mixing patterns in disease spread. 14

These fndings highlight that efective meningitis prevention extends beyond vaccination. Public health interventions should also promote improved indoor ventilation, reduce overcrowding where feasible, minimize exposure to indoor smoke, and strengthen community awareness during the high-risk dry season. Integrating these anthropological and behavioral considerations into meningitis control strategies is essential for reducing transmission and preventing seasonal epidemics across the African meningitis belt. 11,14

Recommendations

1. We need the government, at every level, to adequately prepare all concerned health facilities at the very instant a meningitis outbreak is forecasted, and to make special preparations for children and the elderly 15,16. Meningitis must be combated with systems that prevent it from thriving in its favourable climate 16. The International Coordinating Group should be called upon in times of need 15. Meningitis outbreak can be predicted and the predictions should be met with proper preventive measures 15.
2. Actions should be taken to extend the coverage of the meningitis prediction model. Governmental and non-governmental organisations should work together to see that the model’s coverage extend to areas such as the Congo Basin and the Namibian desert, to further help in meningitis prevention 15.
3. Several insights can still be garnered from Africa’s climatic conditions. These insights can help us in further reducing the occurrence of other climatic-dependent diseases. And this holds for meningitis also, as there are even more critical analyses that can be done on the existing data 17.
4. Direct, rapid medical intervention to stop an active or rising outbreak in its tracks by building immediate herd immunity, cerebrospinal meningitis is highly contagious and spreads through respiratory droplets. Temporarily restricting crowded social events and the movement of known carriers acts as a physical circuit breaker to halt transmission during peak outbreak seasons.18

References

1. World Health Organization. Meningitis [Internet]. Geneva: World Health Organization; 2025 [cited 2026 Jul 14]. Available from: https://www.who.int/news-room/fact-sheets/detail/meningitis
2. Yaka P, Sultan B, Broutin H, Janicot S, Philippon S, Fourquet N. Seasonality of meningitis in Africa and climate forcing: aerosols stand out. J R Soc Interface. 2008;5(22):991–1000. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC3565698/
3. Dione C, Talib J, Bwaka AM, Kamga AF, Bita Fouda AA, Hirons L, et al. Improved sub-seasonal forecasts to support preparedness action for meningitis outbreak in Africa. Climate Services. 2022;28:100326. doi:10.1016/j.cliser.2022.100326. Available from: https://www.sciencedirect.com/science/article/pii/S2405880722000449
4. Agier L, Martiny N, Thiongane O, Mueller JE, Paireau J, Watkins ER, et al. Towards understanding the epidemiology of Neisseria meningitidis in the African meningitis belt: a multi-disciplinary overview. International Journal of Infectious Diseases. 2017 Jan 1;54:103–12. doi:10.1016/j.ijid.2016.10.032
5. Agier L, Deroubaix A, Martiny N, Yaka P, Djibo A, Broutin H. Seasonality of meningitis in Africa and climate forcing: aerosols stand out. J R Soc Interface. 2013 Feb 6;10(79):20120814. doi:10.1098/rsif.2012.0814 PubMed PMID: 23221989; PubMed Central PMCID: PMC3565698.
6. Yarber AY, Jenkins GS, Singh A, Diokhane A. Temporal Relationships Between Saharan Dust Proxies, Climate, and Meningitis in Senegal. Geohealth. 2023 Feb 7;7(2):e2021GH000574. doi:10.1029/2021GH000574 PubMed PMID: 36776988; PubMed Central PMCID: PMC9905059.
7. Martiny N, Chiapello I. Assessments for the impact of mineral dust on the meningitis incidence in West Africa. Atmospheric Environment. 2013 May 1;70:245–53. doi:10.1016/j.atmosenv.2013.01.016
8. Pandya R, Hodgson A, Hayden MH, Akweongo P, Hopson T, Forgor AA, et al. Using Weather Forecasts to Help Manage Meningitis in the West African Sahel [Internet]. 2015 Jan 1. doi:10.1175/BAMS-D-13-00121.1
9. The Role of Weather in Meningitis Outbreaks in Navrongo, Ghana: A Generalized Additive Modeling Approach | Journal of Agricultural, Biological and Environmental Statistics | Springer Nature Link [Internet]. [cited 2026 Jul 15]. Available from: https://link.springer.com/article/10.1007/s13253-012-0095-9
10. Mueller JE, Gessner BD. A hypothetical explanatory model for meningococcal meningitis in the African meningitis belt. Int J Infect Dis. 2010;14(7):e553-e559.
11. Kristiansen PA, Greenwood BM, et al. Incidence, carriage and case-carrier ratios for meningococcal meningitis in the African meningitis belt: a systematic review and meta-analysis. PLoS One. 2015;10(2):e0116533.
12. Cooper LV, Kristiansen PA, Christensen H, Trotter CL. Meningococcal carriage by age in the African meningitis belt: a systematic review and meta-analysis. Epidemiol Infect. 2019;147:e228.
13. Trotter CL, Greenwood BM. Meningococcal carriage in the African meningitis belt. Lancet Infect Dis. 2007;7(12):797-803.
14. MenAfriCar Consortium. Meningococcal carriage in the African meningitis belt. Trop Med Int Health. 2013;18(8):968-978.
15. Dione C, Talib J, Bwaka AM, kamga AF, Fouda AAB, Hirons L, et al. Improved sub-seasonal forecasts to support preparedness action for meningitis outbreak in Africa. Elsevier's Climate Services journal. 2022 October 14; 28: 10.
16. Abdullahi AH, Sawa BA, Saleh M. An Assessment of the Influence of Climate Variability on the Occurrence of Meningitis in Kano State, Nigeria. Sahel Journal of Geography, Environment & Development. 2023 June 1: 4; 8.
17. Cliff M, Jahn S, Fouda AB, Latt A, Lingani C, Trotter C. Re-examining the meningitis belt: associations between environmental factors and epidemic meningitis risk across Africa. medRxiv. 2025 February 26; 31.
18. Dukić, V., Hayden, M., Forgor, A.A. et al. The Role of Weather in Meningitis Outbreaks in Navrongo, Ghana: A Generalized Additive Modeling Approach. JABES 17, 442–460 (2012). https://doi.org/10.1007/s13253-012-0095-9