THURSDAY, Nov. 3, 2016 (HealthDay News) -- Mutations in the Ebola virus boosted its ability to infect people during the 2013-2016 epidemic in West Africa, two independent teams of researchers say.

By the time the epidemic ended, more than 28,000 people had been infected and more than 11,000 had died. The authors of the studies wanted to determine if there were any genetic changes in the Ebola virus in response to infection in such a large number of people.

"Ebola virus is thought to circulate in an unknown animal reservoir and to only rarely cross over into people. When the virus does cross over, the effect has been devastating to those people who are infected. Until recently, the human disease outbreaks have been short lived, and the virus has had little opportunity to adapt genetically to the human host," said Dr. Jeremy Luban. He is co-author of one of the studies and a professor at the University of Massachusetts Medical School.

The research teams said they found mutations that increase Ebola's ability to infect humans and other primates. It's possible these mutations increased the spread of the virus during the epidemic.

"If you introduce a virus into a new host, like humans, it may need to adapt to better infect and spread in that host," said Jonathan Ball, co-author of the other study and a virologist at the University of Nottingham in England.

Both studies were published Nov. 3 in the journal Cell.

One particular mutation emerged early in the epidemic just as there was a large spike in the number of cases, and it soon became the dominant virus type circulating in the outbreak, the scientists said.

The two research teams are now trying to learn more about how these new mutations make the Ebola virus more infectious in people.

"It's important to understand how these viruses evolve during outbreaks. By doing so, we will be better prepared should these viruses spill over to humans in the future," Luban said in a journal news release.

More information

The U.S. Centers for Disease Control and Prevention has more on Ebola.