By Ania Lichtarowicz
BBC News health reporter
The first vaccine to protect monkeys against Ebola and Marburg viruses has been developed by scientists from Canada, the United States and France.
Some 120 people died from Ebola in north-western Congo in 2003
The study could advance research into finding treatments for use in humans.
Both Ebola and Marburg cause haemorrhagic fever - massive internal and external bleeding - which can kill up to 90% of those infected.
Angola is continuing to fight the outbreak of Marburg, while cases of Ebola have been reported in Congo.
There are no vaccines and no drugs available against the deadly viruses.
But this latest research - published in the Nature Medicine journal - does show real potential for protection against these diseases.
Scientists adapted another type of virus to carry proteins from the Ebola and Marburg viruses.
This modified virus was injected into macaque monkeys who were later exposed to the disease-causing pathogens.
Just a single injection completely protected the monkeys.
The initial data is so encouraging say the researchers that the technique could be used against other emerging viruses and may even lead to a trial vaccine being developed for humans.