WASHINGTON, United States (AFP) — The Ebola virus is often deadly, but not always, and a study on mice yesterday suggested that genetics may play a role in the severity of the illness.

At a high-security, state-of-the-art biocontainment laboratory in Hamilton, Montana, scientists infected mice with a mouse form of the same species of the Ebola virus that is sweeping West Africa.

Seventy per cent of the mice got sick, and more than half of this group died, some due to liver inflammation and others due to internal haemorrhage, according to the study in the US journal Science.

About 19 per cent of the mice lost weight initially but then regained it in two weeks and made a full recovery.

The remaining 11 per cent showed a partial response to the virus and less than half in this group died.

Scientists said the variability in outcomes resembled what has been seen in the human epidemic sweeping West Africa this year, killing more than 4,900 people and infecting more than 13,000.

They were also able to find associations in disease outcomes and mortality rates according to specific genetic lines of mice.

“Our data suggest that genetic factors play a significant role in disease outcome,” said Michael Katze from the University of Washington Department of Microbiology.

Those that died showed more activity in genes that promoted blood vessel inflammation and cell death, leading to more serious illness.

Those that survived tended to show more activity in genes responsible for blood vessel repair and making infection-fighting white blood cells.

Specialised types of liver cells might have also helped stop the virus from reproducing, the study said.

“We hope that medical researchers will be able to rapidly apply these findings to candidate therapeutics and vaccines,” Katze said.

Similar observations about the link between genes and outcomes have been made in many different viruses, so the finding should not come as a surprise in Ebola, said Andrew Easton, professor of virology at the University of Warwick.