Baz Ratner / Reuters Health workers carry the body of a suspected Ebola victim for burial at a cemetery in Freetown, Sierra Leone, December 21, 2014.

The Ebola outbreak that devastated West Africa in 2014 was a product of multiple factors, including a population that relies increasingly on global travel, poverty and inadequate public health infrastructure on the ground and local burial practices that conflicted with medical advice.

Now, we know about another factor that helped the outbreak spread: the virus mutated.

Mutation is standard among viruses, and according to two cell model studies published in the journal Cell in November, an Ebola mutation may have allowed the virus to infect humans more easily than the original.

The 2014 outbreak resulted in approximately 70 times more Ebola cases than any previous outbreak, according to U.S. Centers for Disease Control and Prevention data referenced in one of the new studies. And at least 90 percent of those infected contracted the mutant Ebola virus, The Washington Post reported.

“The largest difference we saw was about a fourfold increase in the number of cells infected,” Jeremy Luban, author of one of the studies and virologist at the University of Massachusetts Medical School told NPR.

“When you’re talking about a virus that could kill you, this is a pretty scary number.”

In the end, the 2014 Ebola outbreak claimed 11,310 lives, more than any other previous outbreak, according to CDC.