Genome analysis of Ebola epidemic uncovers epidemiological patterns

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International collaborative research to analyze the entire database of Ebola virus genomes from the 2013–2016 outbreak in West Africa has uncovered insights into driving factors, such as cities. The research has led to calls for real-time sequencing and data sharing as a standard in future disease outbreaks.

The study, published recently in Nature, has reported that the West African epidemic unfolded in small, overlapping outbreaks with surprisingly few infected travelers sparking new outbreaks.

Lead author, Gytis Dudas (Fred Hutchinson Cancer Research Center, WA, USA) explained: “We calculated that 3.6%of cases traveled, basically meaning that if you were able to focus on those mobile cases and reduce their mobility, you might have had a disproportionate effect on the epidemic.”

The team collectively analyzed 1610 Ebola virus genomes, representing more than 5% of known cases and the largest sample size for a single human epidemic. The researchers then assessed 25 factors they hypothesized could have been factors affecting the spread and duration of the 2013–2016 epidemic.

They discovered that cities played a major role in the size of this epidemic compared with previous outbreaks in sparsely populated regions. In addition, the team demonstrated that the distance between cities was also an important factor; the shorter the distance, the more likely it was that infected travelers arrived and seeded infection.

However, they reported that some of the other variables investigated, for example, economic output, shared language and climate, were not significantly associated with the growth of the epidemic.

This study is the first to investigate how Ebola spread, proliferated and declined across high-burden countries, and has demonstrated that genome-analysis data combined with information on population size, travel distances, geography and other factors could help uncover which factors influenced the epidemic’s spread and duration. This in turn could help to direct treatment and interventions.

Sources: Dudas G, Carvalho LM, Bedford T et al. Virus genomes reveal factors that spread and sustained the Ebola epidemic. Nature. doi:10.1038/nature22040 (2017) (Epub ahead of print); www.fredhutch.org/en/news/center-news/2017/04/a-big-picture-look-at-the-worlds-worst-ebola-epidemic.html

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