Research undertaken by the University of Nottingham and the University of Massachusetts analysed the genetic code of almost 2,000 Ebola virus samples, finding that a change on the surface of the virus allowed it to lock on to human cells more easily. The research also found that as the virus adapted to infect people, it became less able to infect natural host species, like fruit bats.
The study found that people infected with the new mutant form of the virus were more likely to die than those infected with the original version, countering the theory that as Ebola spent more time in people it would evolve to become less deadly in order to help it spread.
Dr Wright, commented: "One of these changes occurred around the time when the number of cases started to dramatically increase. This gives rise to the possibility that this change could have been pivotal in the virus' ability to infect humans and ultimately the scale of the outbreak.
"However, these studies do not definitively answer the latter question."