Adrien Deroubaix PhD thesis

Impact of desert dust and climate on the meningitis epidemics in the Sahel

Beginning of the thesis: october 2009

Funding: climate-environment-society consortium, ADCEM project

Supervisors : Sylvie Thiria (équipe modélisation et méthodes statistiques avancées, LOCEAN) & Nadège Martiny (équipe CRC, laboratoire Biogéosciences)

 

Abstract

Thumbnail imageMeningitis epidemics are a major public health problem in several African countries belonging to the “meningitis belt”. The dry season in the Sahel lasts from November to May, when the Harmattan wind, coming from the Sahara, carries dust at the ground level into this region. The period of maximum meningitis incidence (i.e. the ratio of the number of meningitis cases and the respective population) coincides with the period of highest temperatures and dust concentrations in the Sahel. A database with weekly epidemiological and geophysical parameters has been created at different spatial scales (district, region, national) based on four ERA-interim variables (temperature, humidity, wind force and wind angle) and the Aerosol Index (AI). In a first step, the AI has been compared to dust concentration measurements at the ground level and thus been validated in the context of dust impact studies on health. At the national scale, a time-lag of several weeks has been shown between the increase of the aerosol optical thickness and the meningitis incidence. This time-lag was also found using the AI at the national scale and at the district scale. During the epidemic years, a statistical model of the weekly meningitis incidence has been established based on temperature and ground dust concentration. This model explains 1/3 of the variance of the observed meningitis incidence. Moreover, the onset dates of the outbreaks are well retrieved at the country scale (R = 0.94). These results show that climate and Saharan dust must be taking into account to explain the seasonality of meningitis epidemics.

 

Key words

epidemics ; meningitis ; aerosols ; desert dust ; climate ; Sahel

 

Jury

Hervé Le Treut – président
Gil Mahé – rapporteur
Jacques-André Ndione – rapporteur
Isabelle Chiapello – examinateur
Hélène Broutin – examinateur
Bernard Fontaine – examinateur
Sylvie Thiria – supervisor
Nadège Martiny – cosupervisor