Climate Change And Unsustainable Development Can Increase Risk Of Ebola Outbreaks

The risk of future Ebola outbreaks could be greatly reduced by more aggressive climate mitigation measures along with rapid progress on the Sustainable Development Goals, according to a new paper published in Nature Communications. Led by researchers at University College London, the article is the first study to examine the potential effects of global warming and the ecology of the Ebola virus (EVD) circulation among animal “hosts” on future Ebola outbreaks in human populations.

The study, Impacts of environmental and socio-economic factors on emergence and epidemic potential of Ebola in Africa, is a complex modelling exercise that demonstrates how progress on climate mitigation and strengthened health systems could reduce the impact of future outbreaks of the major Ebola virus strains that are endemic to key parts of Africa. Conversely, future outbreaks are likely to expand greatly their geographic reach if climate mitigation measures stall and progress on sustainable development is weak, according to the simulations, which were built around past experiences with outbreaks around Africa.

Under current trends of “business as usual emissions” and unsustainable development, which exacerbates poverty and stresses health systems, there could be a 14.7% increase in the geographic span of areas at risk of Ebola outbreaks, the study concludes.  Future Ebola outbreaks could thus reach countries such as Ghana and Nigeria that were relatively unscathed by the West African epidemic of 2014-2016 (which was focused around Guinea, Sierre Leone and Liberia). Uganda, Kenya, and Rwanda were also noted as areas in East Africa that could see potential Ebola outbreaks in business-as-usual scenarios.

Conversely, effective climate mitigation and sustainable development measures could actually reduce the geographic span of major outbreaks, decreasing the total area at risk of large-scale epidemics by 47%.

Change in future risk of EVD cases caused by Zaire Ebola virus (EBOV) for 2070. Maps represent mean change in per grid cell (0.0416°—5.6 km at equator) Ebola case probability is higher in red and lower in blue. Rows and columns show all reasonable combinations of the different scenarios of global change with the lower right indicating the best-case scenario (High climate mitigation, high sustainable development) and the top left indicating the worst-case scenario (“Business as usual emissions” and unsustainable development).

Climate change is a driver of EVD because it is is associated with expansion of the range of animal EVD hosts such as fruit bats, which prefer warm, wet climates and are believed to constitute an important animal reservoir for the virus.

Climate change and related environmental changes such as deforestation, urbanization and land use changes associated with agricultural expansion are all known factors that can intensify human contact with a range of disease-carrying animals, which are harbored by natural ecosystems. In the case of EVD, bush-meat hunting could also increase infection risks, the authors noted although this factor was not included in their model due to insufficient data. Climate-driven migration may also increase person-to-person disease transmission, related to migration from areas of drought and extreme weather, as well as further stress already overburdened health systems. However, more data on such interactions is needed to definitively predict the effect of increased human-animal contact on EVD outbreak risk.

The authors soberly note that current global commitments for climate action will be unlikely to induce the “wholesale change” in climate change drivers that would be required to also decrease risks of EVD. Therefore, they suggest that efforts to decrease poverty in Central and Western Africa, while expanding access to healthcare resources appears to be the most realistic approach to reducing future EVD disease risk regionally and globally.

Image Credits: Nature.