Using advanced genomic sequencing technology, the origin of the latest Ebola outbreak has been traced to a single transmission from animal to human that spread during the course of a funeral. The results of this work have been published in the journal Science.

Researchers from the Eli and Edythe L. Broad Institute of the Massachusetts Institute of Technology (MIT) and Harvard University and the Sierra Leone Ministry of Health and Sanitation collaborated to analyze 99 Ebola virus genomes from 78 patients diagnosed with Ebola in Sierra Leone during the first 24 days of the outbreak using deep sequencing. Compared to previous Ebola outbreaks, the 2014 Ebola virus genomes have more than 300 genetic alterations; sequencing variations also indicate that the current outbreak stemmed from a single transmission from animal to human that spread over the course of several months. It is speculated that the West African variant diverged from Middle African genomic lineages around 2004, crossed from Guinea to Sierra Leone in May 2014, and has sustained human-to-human transmission ever since with no additional animal sources.

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The outbreak was first reported in February 2014 in Guinea, West Africa and spread in March into Liberia, in May to Sierra Leone, and in late July to Nigeria. An epidemiological link between the first reported case of Ebola in Sierra Leone and the funeral of a traditional healer who had treated an Ebola patient in Guinea was discovered by the Sierra Leone Ministry of Health and Sanitation, which then led to 13 additional Ebola cases in females who had attended the same funeral.

Five of the co-authors of the study contracted Ebola and passed away prior to the publication of the manuscript. These co-authors are praised in the article for their contributions to the research and public health.

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