Marburg disease was recognised in 1967, when an outbreak affected workers in scientific units in Marburg and Frankfurt in Germany, and Belgrade m Yugoslavia. Altogether, 25 workers were infected all of whom had contact with the blood, organs or cell-cultures derived from a batch of imported monkeys (African green monkeys-Cercopithecus aethiops) from north-western Uganda. Six secondary cases occurred five, in healthcarers who had contact with the body fluids or blood of the primary cases. One secondary case was the wife of a patient who became ill 83 days after the onset of his illness, after he returned home, in convalescence. The patient was found to be excreting virus in his semen.

The first outbreak of Marburg disease to be recognised in Africa was in South Africa in 1975. The index case was a young Australian man who had hitch-hiked through Zimbabwe. He died in a Johannesburg hospital and shortly afterwards his companion and a nurse who had cared for him fell ill with the same disease, but both recovered. There was evidence of virus persisting in the body; it was cultured from fluid aspirated from the anterior chamber of the eye of one of the cases 80 days after the onset of illness. Two further episodes were reported in 1980 and 1987 amongst European tourists visiting the Kitum cave, Mt. Elgan in Kenya, and a third in Zimbabwe in 1982.

A person who had recently travelled from Africa fell ill in Sweden in 1991. Serological evidence suggested Marburg virus infection but no virus was recovered from blood or body fluids and the patient recovered.

The Marburg virus and its detection

Marburg virus is a member of the family of filoviruses. It behaves similarly to Ebola and is readily detectable in the blood and tissues of infected individuals. An early positive PCR test may confirm the diagnosis, but a negative, test does not refute it. IgM antibodies are detectable by ELISA within the first week of illness, and cell culture in VERO cells can be performed using blood, urine or fresh tissue samples.

Clinical Features

The incubation period of Marburg disease in the European outbreak was 3-9 days. The course of the illness is similar to that of Ebola, though Marburg virus infection tends to be less severe and has a lower case fatality rate.

Methods of Transmission

As with Ebola virus, the natural reservoir of Marburg virus is unknown but acquisition of the infection by monkeys may bring it into contact with man. Once successfully transmitted to humans, Marburg is capable of person-to-person spread, most commonly by contact with infected blood. Aerosol transmission has not been described in the clinical setting, but it would be unwise to disregard the possibility of this occurring when the patient is seriously ill with pulmonary involvement. Similarly, in the laboratory and other experimental settings, aerosol transmission between animals has not been entirely excluded.

Treatment

No specific treatments (antiviral drug, cytokine or vasoactive agent) have been shown to date to influence the course of Marburg infection. Treatment is generally a matter of applying intensive supportive measures.

Public Health Measures

Marburg disease is notifiable or reportable in most Western countries. Cases or outbreaks should also be reported to the World Health Organisation. Marburg virus is a hazard category 4 virus, and should be handled in a containment level 4 laboratory.

Large outbreaks of Marburg fever have not been recognised in endemic areas, but would be managed in a similar way to outbreaks of Ebola fever, if they occurred. When sporadic (imported or laboratory-acquired) cases are suspected in non-endemic countries, strict isolation and barrier nursing are recommended, and the handling of biological specimens (especially for diagnosis and patient management) is carried out according to regulations governing risk assessment and control.

Contacts of cases, or individuals with exposure in laboratories are placed under health surveillance for 21 days after their last exposure to infection. If they become feverish, they undergo risk assessment and may be admitted to strict isolation pending the results of diagnostic tests.