Marburg haemorrhagic fever is a serious disease with a high mortality rate and is caused by a virus belonging to the same family as the virus which causes Ebola virus haemorrhagic fever. The viral particles appear as long filaments under the electron microscope, sometimes rolled into unusual shapes, hence the name of the family: the Filoviridae. They are amongst the most virulent pathogens known to human beings.
Although they are caused by two different viruses, it is almost impossible to distinguish between the two diseases clinically. They are rare but cause spectacular outbreaks, with high mortality rates. The attention of health authorities in the past was only drawn to these outbreaks when inadequate infection control measures increased transmission in health care establishments.
There is no vaccine or specific treatment for either of these two diseases. Despite years of detailed investigations with tests on hundreds of animals, insects and plants, no animal reservoir or environmental source for either of these two viruses has been identified. Monkeys can be infected, although they are not considered to be a viable reservoir as almost all infected animals die too quickly to sustain survival of the virus for any length of time. Human beings are not thought to belong to the natural cycle of transmission. They are infected accidentally.
Causative agent. Marburg virus, belonging to the Filoviridae family.
Geographical distribution. Outbreaks and sporadic cases have been reported in Angola, the Democratic Republic of Congo, Kenya and South Africa (in a person who had recently travelled to Zimbabwe). The first outbreaks in Germany and in the former Yugoslavia in 1967 were associated with two laboratory workers, working on African Green monkeys (Cercopithecus aethiops) imported from Uganda.
Transmission. Transmission of the virus between people requires very close contact with an affected patient. Contact is required with blood or biological fluids (faeces, vomit, urine, saliva, respiratory secretions), particularly if they contain blood and high concentrations of the virus. They can be transmitted in semen for up to seven weeks after clinical recovery. Infections due to these fortuitous cases of contact are considered to be exceedingly rare. The small number of fortuitous cases due to contact suggest that transmission from aerosol droplets breathed out from the respiratory tract is ineffective, if indeed it actually occurs. No transmission occurs during the incubation period. Patients appear to be most infectious during the severe phase of the disease, which is associated with its haemorrhagic effects. Close contact with a severely affected patient, from health care at home or in hospital, and certain funeral practices, are the common means of infection. Patients in whom transmission occurs from contaminated injection equipment or accidental needlestick injuries develop a more serious illness, deteriorate faster and may have a higher mortality rate.