FLICKR, CDC GLOBALThe Ebola virus still circulating in West Africa may not be the super-mutator that some researchers have thought. According to a study published this week (March 26) in Science, the virus is evolving at a rate typically seen in animals—about half as fast as estimated by a study last year.
“It hasn’t become increasingly lethal or increasingly virulent,” coauthor David Safronetz, a staff scientist for the Laboratory of Virology at the National Institute of Allergy and Infectious Diseases (NIAID), told The New York Times. “The virus—it’s doing what it’s always done.”
“This is some good news for the development of interventions,” NIAID Director Anthony Fauci told NPR’s Goats and Soda. “The data also indicate it’s quite unlikely the virus will mutate and change its way of transmission.”
Last August, Pardis Sabeti of Harvard University and the Broad Institute, and her colleagues sequenced the genomes of 99 Ebola samples taken from the blood of 78 patients in Sierra Leone, identifying evidence that the virus was rapidly mutating—as much as twice as fast during the ongoing outbreak than the virus’s normal rate of change in its animal host. Concern spread that the high mutation rate could make the virus more harmful or more easily transmissible over time, though there was no evidence that this was the case. Indeed, in November, researchers at the University of Texas at Austin published a paper on the bioRxiv preprint site cautioning that more sequence data would be required to confirm how fast the virus was changing.
In the new study, Safronetz and his colleagues found that, based on two small clusters of Ebola cases in Mali, the virus was changing at a rate about half of that estimated by Sabeti’s team, on par with the known mutation rate of Ebola in its animal reservoir. But some emphasize that the difference between the two estimates may simply be attributed to technical details of the models used.
“It is simplistic to think that these minor differences in rate estimates will translate into radically different evolutionary trajectories,” University of Sydney evolutionary biologist Edward Holmes told Nature.