Ebola virus evolution tracked by genetic data

SAN JOSE, Calif. — Genetic data are beginning to reveal how the Ebola virus causing the epidemic in Western Africa is evolving.

Scientists have deciphered the entire catalog of genetic data for 96 Ebola viruses taken from patients infected between June and September 2014. The results show that one particular clade, or type of the virus, is dominant among patients in Sierra Leone, suggesting that two other clades that dominated early on in the outbreak have died out. This third clade appears to have evolved starting with a single mutation in the genetic catalog, or genome, of the virus, said Stephen Gire of Harvard University and the Broad Institute in Cambridge, Mass. He presented the preliminary findings February 14 at the annual meeting of the American Association for the Advancement of Science.

The particular virus responsible for the current Ebola outbreak in West Africa is Zaire ebolavirus. An earlier analysis of 99 genomes collected within three weeks of the outbreak’s start in Sierra Leone (SN: 9/20/14, p. 7) found that the virus can develop mutations that reduce the effectiveness of an experimental therapy based on short interfering RNAs, or siRNAs, Gire said. Having data from more genomes will allow scientists to identify additional mutations that can thwart the therapy — information that should help in finding ways to make the therapy more effective.

Gire said several hundred more genomes should be cataloged and made available within the next month. The data are collected and available to the public at virological.org.

Editor’s note: This story was updated on February 17, 2015, to clarify when the patients from whom the 96 Ebola viruses were collected were infected.