This Might Be Why Some Survive Ebola

Scientists in a biosafety level 4 lab have discovered that genetics are likely involved in how susceptible someone is to Ebola, finds a new mice study published in the journal Science.

Why some people survive Ebola and others do not, even when they’re treated in the same conditions, is a question that’s long intrigued researchers. The current outbreak has also revealed that humans show symptoms of the disease differently; a significant number do not present hemorrhagic fever symptoms like heavy diarrhea, vomiting and bleeding before death.

So far, researchers have primarily used monkeys to study the Ebola virus, but in the new study, the researchers discovered that a genetically diverse population of mice had wide variations in their responses and symptoms to the Ebola virus—similar to how humans have reacted. It’s notable because mice very rarely have similar immune responses to humans, which is why discoveries made in mouse models are evaluated skeptically.

When the researchers infected the mice with Ebola, they found that some of the mice survived with mild disease symptoms, some died, and some died with severe hemorrhagic fever symptoms similar to those observed in humans. Researchers Michael G. Katze and Angela L. Rasmussen of the University of Washington also identified a few potential genetic pathways that might differ in mice who survive the disease versus those who die from it. The hope is that these pathways could help researchers develop drugs for the disease.

“We now have a model that represents the human Ebola disease that we could test vaccines in, we could test novel therapeutics in, and we also could start getting information about the genes that are responsible for the resistance to Ebola and the susceptibility to Ebola,” said Katze in a video about the study. Before the researchers can make the leap to developing drugs for humans, they will have to confirm that the pathways also exist in humans and work in the same way. But the new research is a starting point.

The team started studying the progression of the Ebola virus in mice a few years ago, before the current outbreak of Ebola started in West Africa. Only a handful of of scientists work in the few high-security containment labs in the United States. The training, Katze told TIME, is intense and requires psychological testing. “We’ve been studying Ebola for almost a decade. We’ve always been interested in Ebola because it’s a very interesting virus. It’s like the rockstar of viruses,” Katze told TIME in early October.

Read on for more about the scientists’ emerging Ebola research.