An overview of bacterial meningitis epidemics in Africa from 1928 to 2018 with a focus on epidemics "outside-the-belt"

Abstract

Background: Bacterial meningitis occurs worldwide but Africa remains the most affected continent, especially in the "Meningitis belt" that extends from Senegal to Ethiopia. Three main bacteria are responsible for causing bacterial meningitis, i.e., N. meningitidis (Nm), S. pneumoniae and H. influenzae type b. Among Nm, serogroup A used to be responsible for up to 80 to 85% of meningococcal meningitis cases in Africa. Since 2000, other Nm serogroups including W, X and C have also been responsible for causing epidemics. This overview aims to describe the main patterns of meningitis disease cases and pathogens from 1928 to 2018 in Africa with a special focus on disease conditions "out-of-the-belt" area that is still usually unexplored. Based on basic spatio-temporal methods, and a 90-years database of reported suspected meningitis cases and death from the World Health Organization, we used both geographic information system and spatio-temporal statistics to identify the major localizations of meningitis epidemics over this period in Africa.

Results: Bacterial meningitis extends today outside its historical limits of the meningitis belt. Since the introduction of MenAfrivac vaccine in 2010, there has been a dramatic decrease in NmA cases while other pathogen species and Nm variants including NmW, NmC and Streptococcus pneumoniae have become more prevalent reflecting a greater diversity of bacterial strains causing meningitis epidemics in Africa today.

Conclusion: Bacterial meningitis remains a major public health problem in Africa today. Formerly concentrated in the region of the meningitis belt with Sub-Saharan and Sudanian environmental conditions, the disease extends now outside these historical limits to reach more forested regions in the central parts of the continent. With global environmental changes and massive vaccination targeting a unique serogroup, an epidemiological transition of bacterial meningitis is ongoing, requiring both a better consideration of the etiological nature of the responsible agents and of their proximal and distal determinants.

Keywords: Epidemics; Epidemiology; In- and outside the meningitis belt; Meningitis; Pathogens; Spatial analysis; Time-series.

Fig. 1

Annual meningitis cases (blue bars) and death (red line) in Africa, 1928–2018 (a), annual cases (blue bars) and deaths (red lines) of meningitis reported from 1928 to 2018 in countries within the belt (b) and outside the belt (c). Countries are ranked from left to right according to the number of cases reported

Fig. 2

Spatial distribution of meningitis cases by country in Africa from 1928 to 2018 (Note that meningitis cases information is unavailable for the period 1948–1957). The areas in grey illustrate the different countries belonging to the meningitis belt

Fig. 3

Time-series of bacterial meningitis pathogens identified in Africa from 2000 to 2010 (a) and from 2011 to 2017 after MenAfrivac (b)

Fig. 4

Spatial distribution of different pathogen species and strains causing meningitis in Africa by country from 2000 to 2010

Fig. 5

Spatial distribution of different pathogen species and strains causing meningitis in Africa by country from 2011 to 2017