In conclusion, while viral dissemination was observed in various organs, no shedding of infectious viral particles was noted, and no toxic effect in relation to the MV vaccination was found following one or three IM injections with a clinically relevant dose of MV1-F4, with the same outcomes for the (Schwarz) measles comparator vaccine. Moreover, either vaccine virus replicated predominantly in secondary lymphoid organs and, to a lesser extent, in epithelium-rich tissues. Thus, as expected, introduction of the F4 transgene did not change the toxicological profile, shedding capacity or tropism of the parental strain. Forty-Five Years of Marburg Virus Research In 1967, the first reported filovirus hemorrhagic fever outbreak took place in Germany and the former Yugoslavia. The causative agent that was identified during this outbreak, Marburg virus, is one of the most deadly human pathogens. This article provides a comprehensive overview of our current knowledge about Marburg virus disease ranging from ecology to pathogenesis and molecular biology. Marburg virus (MARV) first appeared in August 1967, when laboratory workers in Marburg and Frankfurt, Germany and Belgrade, Yugoslavia (now Serbia) were infected with a previously unknown infectious agent. The 31 patients (25 primary, six secondary infections) developed severe disease that progressed to a fatal outcome in seven of the cases. An additional case showing symptoms of disease was diagnosed retrospectively (reviewed in [1] ). The source of infection was traced back to African green monkeys (Chlorocebus aethiops) that had been imported from Uganda and were shipped to all three locations. The primary infections ironically occurred when the monkeys were necropsied for the purpose of obtaining kidney cells to culture poliomyelitis vaccine strains. In the remarkable period of less than three months the etiologic agent was isolated, characterized, and identified by the joint effort OPEN ACCESS of scientists in Marburg and Hamburg [2] and was later confirmed by Kunz and colleagues [3] and Kissling and colleagues [4] . The pathogen was named Marburg virus after the city with the most cases and represented the first isolation of a filovirus. Erroneously, a study published in 'The Lancet' claiming that the mysterious disease was caused by rickettsia or chlamydia has frequently been cited as the first report on the causative agent of Marburg virus disease (MVD) [5] .