The relationship between meningococcal meningitis and proximity to bodies of water: a case study of Northern Ghana

Inhabitants of the ‘Meningitis Belt,' an area of sub-Saharan Africa which stretches from Ethiopia to Senegal, are threatened by frequent epidemics of meningococcal meningitis. Epidemics occur in multi-year cycles which include prominent increases in the attack rate of the disease during the middle of the dry season and decreases with the onset of the wet season. While the physiological causes of these seasonal trends are not well understood, they suggest a possible negative relationship between relative humidity and the incidence of meningitis. This study examines the geographic implications of this relationship, focusing on the possible correlation between meningitis incidence and the proximity of a population to a large body of water in northern Ghana. Epidemiological and meteorological data from the region of Navrongo, Ghana were collected in 2010 and 2011. Using a geographic information system (GIS), meningitis cases and seasonal average relative humidity data were mapped and analyzed based on their location relative to the reservoir. The directions of prevailing winds were used to further analyze the epidemiological data by considering the potential impact of advection and diffusion of moisture from the lake. While further studies would be needed to clarify results, the study found a possible trend between the extent of the reservoir's estimated moisture blanket and the decreased incidence of meningitis. As a preliminary step in examining these relationships, this study offers a methodological approach that will aid the further exploration of this and other relationships between meteorological, epidemiological, and geographical factors, along with providing potential ideas for reducing disease incidence.