Marburg virions are 80 nm in diameter and average approximately 800 nm in length, although length can vary up to 14,000 nm. The virion length associated with peak infectivity is 790 nm. Virion lipids reflect the composition of lipids in the host-cell membranes. The virus is classified as a biosafety level 4 agent because of its extreme pathogenicity and the lack of a vaccine or antiviral drug. Marburg is named after the German town in which some of the first cases were described.
Endemic areas appear to be Central and East Africa.
In particular, visitors to the Kitum cave on top of Mt. Elgon have contracted Marburg. Marburg may also have a natural reservoir in Zimbabwe. The natural reservoir for the virus is unknown. Epidemiologists have tested bats, monkeys, spiders and ticks for the virus, but were not able to acquire definitive data. Common factors indicate that the natural reservoir is part of rural Africa.