WEDNESDAY, May 13, 2015 (HealthDay News) -- The deadly Ebola virus has continued to mutate during the West African epidemic, but at the same rate as previous outbreaks, a team of genetic researchers has found.
Genetic analysis of samples taken from 175 Ebola patients in Sierra Leone found the genetic diversity of the virus has increased substantially, the researchers report May 13 in the journal Nature.
Their research reveals a "family tree" of Ebola strains that has emerged as the virus passed from person to person, including seven new lineages that evolved from the original strain that started the epidemic, the study says.
However, the Chinese researchers agree with other recent studies that have concluded Ebola is mutating (changing genetically) at its normal rate.
"Ebola, like all viruses, mutates as it infects individuals," said Dr. Amesh Adalja, a senior associate at the Center for Health Security at the University of Pittsburgh Medical Center. "This study provides evidence that, not surprisingly, during the West African outbreak the virus has mutated at a rate similar to past outbreaks and has formed new lineages."
A study published in March in Science found Ebola samples taken in Guinea also mutating at the same rate as previously observed.
Some public health experts had worried that the current Ebola epidemic -- the worst in history -- would promote increased evolution of the virus, giving it the chance to grow more virulent forms. For instance, some feared the virus, now transmitted through direct contact with infected blood or bodily fluids, would mutate into a form that could spread in the air.
While news from this study provides reassurance that Ebola will not go airborne anytime soon, such new genetic information is also critical in planning for future outbreaks as well as dealing with the ongoing West African epidemic, said Ebola expert Dr. Lee Norman, chief medical officer for the University of Kansas Hospital.
The current epidemic has centered around the nations of Liberia, Guinea and Sierra Leone. More than 11,000 people have died, and as many as 26,700 may have been infected with Ebola, according to the U.S. Centers for Disease Control and Prevention.
"It's not a moot question, where did it come from and where will it go, because that's important for us to understand so we can stay one step ahead of it," Norman said. "Forecasting of disease is imprecise at best, but if you take all that family tree information and map it out over time, it tells us where we should go to head it off at the pass."
New genetic information also provides clues whether vaccines and medications now being developed for Ebola will be effective against future strains of the virus, Adalja said.
"It will be important to understand how these new lineages fare against developing vaccines and antivirals," he said.
However, Adalja emphasized that Ebola's ongoing mutation during the epidemic "is not something that is unprecedented or unexpected, nor able to confer wholly new attributes on the virus."
The World Health Organization declared the end of the Ebola outbreak in Liberia on Saturday, after no new cases of Ebola surfaced over 21 days. That's the virus' maximum incubation period.
Norman said he hopes public health officials in Liberia will remain on guard, given that disease reporting can be sketchy in impoverished countries.
"We wouldn't want to reduce our efforts until we have pretty darned good evidence" that the epidemic is truly over, he said.
More information
For more on Ebola, visit the U.S. Centers for Disease Control and Prevention.
