This negative stained transmission electron micrograph (TEM) depicts a number of filamentous Marburg virions, which had been cultured on Vero cell cultures, and purified on sucrose, rate-zonal gradients. Note the virus’s morphologic appearance with its characteristic “Shepherd’s Crook” shape; Magnified approximately 100,000x. Marburg hemorrhagic fever is a rare, severe type of hemorrhagic fever which affects both humans and non-human primates. Caused by a genetically unique zoonotic (that is, animal-borne) RNA virus of the filovirus family, its recognition led to the creation of this virus family. The four species of Ebola virus are the only other known members of the filovirus family. Marburg virus was first recognized in 1967, when outbreaks of hemorrhagic fever occurred simultaneously in laboratories in Marburg and Frankfurt, Germany and in Belgrade, Yugoslavia (now Serbia).