It has been provisionally referred to as the Bombali virus and is the sixth known species of Ebola.
The virus was discovered in bats and environmental nonprofit group EcoHealth Alliance has warned it has the potential to infect human cells.
They said: “The newly discovered Bombali Ebola virus was found in a bat species of the genus Mops.
“It has the potential to infect human cells, but it’s not known yet if it has been transmitted to people or can cause disease in humans.”
There is no evidence the virus has infected any humans so far.
It was discovered by scientists from the University of California at Davis and Columbia University as part of a US-funded effort to find unknown viruses that have the potential to cause human outbreaks.
Tracey Goldstein, of the One Health Institute at UC Davis, said: “It is really interesting. I think it’s exciting.
“But I think we have a lot of work to do to really understand if it is a pathogen and whether it does or doesn’t pose a threat.”
A scientific paper outlining the discovery is due to be published according to CEO of EcoHealth Alliance Peter Daszak.
The process for announcing the discovery of a new virus is through a peer-reviewed journal.
But Sierra Leone has already been notified of the discovery and wanted to first make the announcement to local press on Thursday.
Mr Daszak said: “They want to preempt negative rumours, and are rolling out education programs to reduce potential for spillover.”
The virus was found in two types of bats of the Molossid family, Angolan free-tailed bats and Little free-tailed bats.
Infected bats were found roosting in people’s homes, according to Goldstein.
Sierra Leone was one of three countries in West Africa to be struck by the devastating Ebola outbreak in 2014 and 2015.
It was caused by the Ebola virus known as Zaire Ebola virus.