The Ebola virus is often deadly, but not always, and a study on mice 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 percent of the mice got sick, and more than half of this group died, some due to liver inflammation and others due to internal hemorrhage, according to the study in the US journal Science.
About 19 percent of the mice lost weight initially but then regained it in two weeks and made a full recovery.
The remaining 11 percent 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.
"While this is valuable information, the data in the paper cannot be directly extrapolated to the human situation and used as a basis for potential therapy at the moment," said Easton, who was not involved in the study.
"Unlike the mice used in the study, humans are extensively outbred and have a large variety of genetic combinations, making assessment of the impact of the genes in humans difficult."
The study also did not account for environmental factors that experts say can affect whether a person lives or dies from Ebola, including the quality of care, their age and how healthy they are when they first become infected.
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