In the prevailing view, ZEBOV arose from long-persistent local strains after increased contact between humans or great apes and an unidentified reservoir host. But Walsh et al. found support for the alternative hypothesis: that ZEBOV had recently spread to the outbreak regions. This is good news because a virus that spreads at a predictable rate in a predictable direction is far easier to control than one that emerges by chance or at the hands of an unknown trigger. The authors modeled the virus's spread based on assumptions of a long-persistent virus versus a recently emerged virus, and tested the predictions of these competing hypotheses using genetic data--gathered from gene sequences taken from human samples at the different outbreak sites--and information on the spatiotemporal dynamics of the outbreaks.
Though the strength of the individual lines of evidence is not conclusive when considered separately, taken together, they support the view that ZEBOV is spreading as a wave from the first epidemic in Yambuku, Gabon. Following its current course, ZEBOV may hit populated areas east of Odzala National Park within 12 years and reach most parks containing large populations of western gorillas in 36 years. Two Ebola outbreaks have already hit human populations west of Odzala, and over the past two years, the largest gorilla and chimp populations in the world, found in Odzala, have been devastat
Contact: Paul Ocampo
Public Library of Science