Identification and analysis of the main drivers for Ebola virus spillover

In relation to the events of the current Ebola outbreak in West Africa, the European Commission requested EFSA to identify the drivers for occasional spillover event of Ebola virus, i.e. the transmission from animals to humans. As part of this work SciencesPo was contracted by EFSA to perform an analysis to visualise and communicate the drivers for spillover of Ebola virus. Based on information available in the peer-reviewed scientific literature, a set of drivers for spillover of infectious diseases was identified and a set of scientific studies was used to structure a corpus of relevant arguments. This corpus was used to analyse the driver network and visualise the driver behaviour. The analysis led to the identification of 40 drivers, connected through 142 linkages. The visualisation of the driver network showed that central drivers involved in spillover are 'Hunting', 'Deforestation/forest fragmentation', and 'Demographic changes of wildlife'. The most frequent driver links identified were 'Deforestation/forest fragmentation' leading to 'Ecosystem changes' and 'Livelihoods resilience' leading to 'Hunting'. Different publication biases may affect this methodology, therefore the findings reported should be interpreted as a representation of the current view of the scientific community on Ebola virus spillover, rather than a comprehensive analysis of drivers of spillover. The methodology used in this report demonstrates a more structured and transparent approach to analysing drivers for infectious diseases. Such visualisations help in apprehending and analysing the whole system, which is complex in nature since it involves bio-ecological, technical, political and socio-economic aspects. Furthermore the understanding of environmental, epidemiological and social factors that lead to such an outbreak may help to prevent future ones.