Published Online: August 15, 2016
The Sahel region of West Africa has the highest incidence of bacterial meningitis in the world. The seasonality of meningitis in the Sahel is well documented, and suggests that climatic factors likely influence disease patterns. However, the key climatic conditions associated with invasive bacterial disease have not been identified, nor have the mechanistic interactions underlying this risk been elucidated.
In a recent study published in The Journal of Allergy and Clinical Immunology (JACI), Jusot and colleagues used a combination of epidemiological data and mechanistic studies in mouse infection models to investigate the link between climate and invasive bacterial disease. The authors conducted daily disease surveillance over 8 years in a Sahel region in Niamey, Niger and integrated this with climatic monitoring data in order to identify risk factors for invasive bacterial disease. Infection models performed in mice with a major bacterial cause of meningitis – Streptococcus pneumoniae – provided direct evidence for the effect of climatic factors on bacterial disease and were used to explore the effects of these factors on both bacteria and host.
Disease surveillance and climate monitoring revealed that high temperatures and low visibility were significant risk factors for bacterial meningitis. Low visibility often occurs following seasonal sandstorms, when the Harmattan winds blow desert dust into the Sahel from the Sahara. Jusot et al. reported that Streptococcus pneumoniae colonized in the upper airways of mice were more likely to spread to disease sites such as lungs, brain or blood following exposure of the mice to inhaled dust or heat. These effects were associated with a reduced ability of white blood cells to direct bacterial killing following exposure to dust, and increased release of damaging bacterial toxins following periods of high temperature.
The study demonstrates that climate can significantly influence patterns of invasive bacterial disease. The researchers suggest that climatic surveillance should be used to forecast invasive bacterial disease epidemics, and simple control measures to reduce particulate inhalation might reduce the incidence of disease in the Sahel.
The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.