Guinea

Spillover or endemic? Reconsidering the origins of Ebola virus disease outbreaks by revisiting local accounts in light of new evidence from Guinea

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James Fairhead, Melissa Leach, Dominique Millimouno

Correspondence to Professor Melissa Leach; m.leach@ids.ac.uk

Summary box

  • That the 2021 outbreak of Ebola virus disease (EVD) in Guinea originated in viral resurgence from a survivor infected 5–7 years ago requires local and scientific accounts of past outbreaks to be revisited.

  • Many past EVD epidemics hitherto considered as independent zoonotic spillovers may have originated from similar flare-ups even after decades, prompting reconsideration of EVD more as an endemic disease over long timescales and wide areas than as a series of discrete epidemics, and accounting for increasing outbreak frequency.

  • Key assumptions in analysis of phylogenetics and of the ecology and drivers of Ebola virus (EBOV) spillover from wildlife hosts such as bats need to be reassessed.

  • More collaborative, respectful approaches with local communities are needed to understand the origins of outbreaks, to address them and to support rather than stigmatise sufferers and survivors.

Introduction

New research finds that the 2021 outbreak of Ebola virus disease (EVD) in Guinea originated in viral resurgence from a persistently infected survivor from the major 2013–2016 epidemic 5–7 years ago prompting an urgent need to re-evaluate whether past EVD epidemics hitherto considered as independent zoonotic spillovers may have had similar origins. Here, we reconsider local accounts from the West African epidemic that trace its origins to people, dismissed until now as implausible. We thus reinterpret existing scientific accounts of other alleged spillovers, finding that several past outbreaks probably originated in persistent infections over even longer latency. By recalibrating the balance between ‘spillover’ and ‘flare-up’, we suggest that EVD manifests less as a series of discrete epidemics and more as an endemic disease in humans over long timescales and wide areas, helping to account for the increasing frequency of episodes.