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Ebola virus evolved at normal rates during epidemic, scientists say

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Chinese scientists report that the Ebola virus responsible for the outbreak in West Africa last year mutated at a normal rate, further alleviating fears that the virus had been able to evolve more rapidly than usual thanks to the prolonged and widespread nature of the epidemic. Ebola, like HIV and influenza, belongs to a class of virus with a high rate of mutation, and scientists had previously warned that it might evolve to become more contagious and, in an extreme scenario, even airborne.

This latest report published in Nature corroborates an earlier study from March, showing that while the virus did mutate as it spread to new areas, it did so within the bounds of expected behavior. Early analyses had suggested that the virus might be evolving at twice the usual rate. The new findings, however, don't make the outbreak itself any less serious — the Nature report states that more than 10,000 individuals are thought to have been killed by the virus, while an additional 25,000 have been infected.

"This is just the virus doing what it does."

The scientists involved in the study, led by epidemiologist Wu-Chun Cao, sequenced 175 virus genomes collected last year in Sierra Leone. The samples were collected between September 28th and November 11th, and in total, were found to contain some 440 new mutations, with most of these occurring in the part of the gene that instructs the virus how to attach itself to human cells. Scientists say that this means it's possible that the virus' evolution was driven by the human immune system, although this pattern of mutation might also simply be down to chance. "This is just the virus doing what it does," David Robertson, a computational biologist based at the University of Manchester in the UK told Nature.