Taco Cowboy sends this report from Vox: One of the big mysteries in the Ebola outbreak in West Africa is where the virus came from in the first place — and whether it's changed in any significant ways. ... In a new paper in Science (abstract), researchers reveal that they have sequenced the genomes of Ebola from 78 patients in Sierra Leone who contracted the disease in May and June. Those sequences revealed some 300 mutations specific to this outbreak. Among their findings, the researchers discovered that the current viral strains come from a related strain that left Central Africa within the past ten years. ... Using genetic sequences from current and previous outbreaks, the researchers mapped out a family tree that puts a common ancestor of the recent West African outbreak some place in Central Africa roughly around 2004. This contradicts an earlier hypothesis that the virus had been hanging around West Africa for much longer than that. Researchers are also planning to study the mutations to see if any of them are affecting Ebola's recent behavior. For example, this outbreak has had a higher transmission rate and lower death rate than others, and researchers are curious if any of these mutations are related to that. ... The scientific paper on Ebola is also a sad reminder of the toll that the virus has taken on those working on the front lines. Five of the authors died of Ebola before it was published.