Ebola virus evolved at normal rates during epidemic: study

The Ebola virus responsible for the outbreak in West Africa last year mutated at a normal rate, according to a new study which suggests the virus has not evolved to become more virulent or deadly.
Researchers led by Wu-Chun Cao, an epidemiologist at the State Key Laboratory of Pathogen and Biosecurity in Beijing, sequenced 175 Ebola virus genomes from people who were infected with the virus, including some who died.
The analysis found that the virus evolved as it spread to new areas.
However, it did not change at a faster rate than it has in past outbreaks - even though those outbreaks were localised to much smaller areas and infected fewer people.

And there is no evidence that Ebola evolved harmful mutations as it spread through Sierra Leone, Nature.Com reported.
"This is just the virus doing what it does," said David Robertson, a computational and evolutionary biologist at the University of Manchester, UK.

Researchers said that the virus continued to evolve more diversity as it spread, meaning that the viruses involved in each localised outbreak evolved independently of each other.
"As the epidemic spread, it created many chains of infections, each of which was mutating in a different direction," said viral geneticist Trevor Bedford at the Fred Hutchinson Cancer Research Centre in Seattle, Washington.

The virus's evolution rate during the current epidemic, and whether it is changing in ways that make it easier to transmit, or more or less lethal, has been hotly debated.
The research was published in the journal Nature.