Filoviridae family of viruses belongs to the order of Mononegavirales. Filoviruses cause hemorrhagic fever often with fatal bleeding and coagulating abnormalities. The name comes from the Latin word filum, which alludes to the thread-like appearance of virus particles. They are single stranded negative sense RNA viruses that target primates. The two genera are Ebola-Reston virus and Marburg virus.

The family was discovered in 1967 when 31 people were infected with the Marburg virus in Germany after working with monkeys imported from Uganda. Seven of those 31 died. All outbreaks since then have occurred in sub-Saharan Africa. Ebola was discovered in 1976 in Zaire and southern Sudan were outbreaks occurred. In 1989 there was one outbreak in Washington, D.C. It was eventually discovered that Reston has no effect on humans. In 2009 Reston infected swine in the Philippines. Swine infection leads to concern that the food supply might get infected leading to the emergence of a REBOV variant that affects humans. Ebola has a mortality rate of 20% to 90% in some of the Zaire Ebola outbreaks. Infection is zoonotic, meaning it can be transmitted from humans to other animals. The natural reservoirs of the virus are not known but bats are suspected.

How it spreads is not fully understood. From animal to human is unknown but between humans transmission occurs through physical contact. Filoviruses are the only known non-retroviral RNA viruses with cytoplasmic replication to have paleoviruses in mammals.