Ebola virus belongs to the Filoviridae family and includes several species, including the Ebola Zaire virus, responsible for an initial outbreak of hemorrhagic fever in 1976 and the current epidemic of West Africa. Fruit bats of tropicalforests are the likely reservoir of this enveloped RNA virus which, following the incidental infection of a human being, is efficiently transmitted from man to man. Ebola virus exhibits a wide cell and tissue tropism and causes a deleterious acute infection leading to severe sepsis burdened with a heavy mortality. During the acute phase, the virus is very abundant in biological fluids where it can temporarily retain its infectivity for several days after death. Virological diagnosis is done mainly by RT-PCR on a blood sample and needs to be practiced in high security conditions. The pathophysiology of the infection allows to consider curative treatments and vaccination which are urgently needed.