Interview: “Climate change is influencing the evolution of meningitis in West Africa”.
“Apport des données satellitaires à la modélisation spatio-temporelle de l'épidémiologie de la méningite en Afrique de l'Ouest dans un contexte de changement climatique : Cas de la Côte d'Ivoire.” This is the theme of Axelle Tano's master's thesis defended on Thursday July 25, 2024 at the Centre Universitaire de Recherche et d'Application en Télédétection (CURAT) of the Université Félix Houphouët-Boigny. Axelle was supervised by CURAT's Dr Adonis Krou Damien. She is a member of the Ecosystem and Population Health (ESA) research group at the Centre Suisse de Recherches Scientifiques en Côte d'Ivoire (CSRS), where she works under the supervision of Dr Diallo Kanny and Dr Richard Yapi.
Axelle's objective in this research was to characterize the link between the incidence of meningitis and climatic parameters (temperature, wind speed, aerosol and relative humidity). To do this, Axelle used satellite data and data from the Direction de l'Information Sanitaire (DIS) in Côte d'Ivoire. These data provide information on the number of cases of meningitis, the year and the localities concerned. Using a visual representation method known as graduated symbology, Axelle classified the number of meningitis cases by region and year, producing a map showing the evolution of meningitis cases by region and year in Côte d'Ivoire. Her study shows that, of all climatic parameters, only temperature has a statistically significant link with meningitis.
Axelle tells us more about her study and the link between climate change and the evolution of meningitis in West Africa in this interview.
1. How is climate change affecting the evolution of meningitis in West Africa, and more specifically in Côte d'Ivoire?
Axelle Tano: Climate change is having an impact on the development of meningitis in West Africa, and more specifically in Côte d'Ivoire, because according to the literature, meningitis is transmitted much more rapidly in the dry season, precisely during the harmattan (Very dry wind blowing from the east or northeast over the Sahara and West Africa.). It can therefore be hypothesized that certain climatic factors during this period are conducive to transmission. These climatic factors include temperature, relative humidity, aerosol index and wind speed, all of which must be present in order to observe a greater number of cases of meningitis. Given that we are confronted with climate change, an evolution of these different parameters in certain regions, allowing for a climate conducive to meningitis transmission, could explain the action of climate change on the evolution of meningitis in West Africa, and more specifically in Côte d'Ivoire.
It's important to remember that the African meningitis belt runs south of the Sahara from the Red Sea to the Atlantic, between isohyets 300 mm and 1100 mm. It lies between latitudes 10 and 15 degrees north.
2. What makes it possible to observe or prove the influence of climate change on the evolution of meningitis?
Axelle Tano: The link between the variability of climatic parameters in a given area and the number of cases of meningitis in that same area over time can be established or proven by looking at the cumulative number of cases detected in the area. In Côte d'Ivoire, the northern half of the country is known as the meningitis hot spot. However, over the last 20 years, high numbers of meningitis cases have increasingly been observed in central and southern Côte d'Ivoire. This could therefore be due to a change in climatic parameters under the effect of a climate change favorable to meningitis transmission.
3. Could you please describe how satellite data are collected and analyzed to provide information on the epidemiology of meningitis?
Axelle Tano: The satellite data was collected in the form of a csv file from three platforms. The first platform is Power access data. The second is Google earth engine and the third is Giovanni. The data were collected and then interpolated, i.e. assigned numerical values from known points (the greater the number of known points, the greater the interpolation) using the Inverse Distance Weighting or IDW technique. This is a spatial interpolation method, a process that assigns a value to any point in a space from a set of known points. The data collected correspond to the place and date at which the cases of meningitis were reported. This will enable us to establish the link between these different climatic parameters and the incidence of the disease. Finally, we model the situation using the negative binomial regression method. This method is most often used when we have count data and a variance higher than the mean (over dispersion). It is performed using the glm.nb function included in R software.
4. Why is modeling important for health research and intervention in Africa?
Axelle Tano: A model is a simplified representation of a real system in order to meet a need. Modeling approaches in healthcare are important and complementary because they enable us to understand the distribution, dynamics and link between disease and climatic parameters in our case. They can also be useful for predicting the presence of disease and the risk of transmission, to help decision-making.
5. What are the prospects for research and practice in the use of satellite data in the fight against meningitis in West Africa in a context of climate change?
Axelle Tano: As far as prospects are concerned, we propose to resume the study on a finer scale (spatial and temporal) and to carry out a mapping study of the risk of meningitis in Côte d'Ivoire. This study will also need to be carried out on a larger scale, even 30 years, in order to better appreciate climate change in the evolution of the various climatic parameters. As part of my Master's degree, I used data from a short period (six years). However, as part of the VIMC2 project on which I'm working with Dr Yapi and Dr Diallo and our British collaborators at Cambridge University, we plan to extend the work to a larger number of years (we've already had the data since 2002) and also to other countries in the African meningitis belt, such as Guinea and Mali. In addition to this, it would be beneficial to produce a meningitis risk map for Côte d'Ivoire, which would enable us to bring together a large number of parameters that play a part in the occurrence of meningitis.
6. What is your message to young women who think they can't do scientific research?
Axelle Tano: First of all, I'd like to say that scientific studies aren't just for those who love numbers and formulas. They're for anyone who's curious enough to understand phenomena (their creation, evolution, risks or distribution, etc.) and has the courage to look for answers. Scientific research is not the prerogative of a specific group. It's important not to limit yourself to gender-related fear or doubt. You may be a woman, but your ideas can open doors to crucial discoveries! Don't be afraid to fail, be courageous, learn and improve every day. Above all, believe in yourself!
