Marburg virus is highly fatal, with a mortality rate of around 50%, though it has reached up to 90% in some outbreaks

A rare, highly contagious Ebola-like virus has claimed eight lives in Rwanda, and U.S. health officials are closely monitoring the outbreak. Marburg virus causes a rare hemorrhagic fever that has no authorized vaccine or treatment.

Rwanda has reported nine deaths from its first-ever Marburg virus outbreak and confirmed 18 patients are in isolation, according to its health ministry.