In 1967, researchers were preparing cultures grown from kidney cells harvested from African Green (Cercopithecus aethiops) monkeys that had been imported from Uganda.1,2,3 A mystery disease struck 27 laboratory workers in Germany and what was then Yugoslavia who had been exposed to the monkeys. Seven laboratory workers died. The workers spread the infection to four other people, including one of their wives who became infected during sex. None of the secondary cases died.1
At first, researchers suspected yellow fever. But they isolated a pathogen that was ‘quite distinct from any other known viruses’.1 Electron micrographs revealed a pathogen resembling ‘a bowl of spaghetti’.1 Researchers named the pathogen after the German town where the deadly disease was first identified: Marburg virus.1
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The first reported cases of Marburg virus in Africa emerged 8 years later, although previous outbreaks probably went unrecorded.1,2 In February 1975, two Australians touring Zimbabwe became ill and entered South Africa. A nurse caring for the couple also fell ill. One of the Australians died.1 Since then health services – often relatively under-resourced – in Angola, the Democratic Republic of the Congo, Equatorial Guinea, Ghana, Guinea, Kenya, Tanzania and, most recently, Rwanda managed outbreaks and sporadic cases of Marburg virus disease.3,4,5
Despite health services’ best efforts, the fatality rate for Marburg virus ranges from 23% to 90%.3 Indeed, Marburg virus is a Category A bioterrorism agent, which includes the most lethal pathogens, alongside, for example, anthrax, botulism and plague.3 So, should we be worried?
Jump the barrier
Marburg, a single stranded RNA virus, is a member of the filoviridae family of viruses, which also encompasses Ebola and Bombali. Ebola is, of course, highly lethal. Bombali, in contrast, seems to have a low potential to cause disease in humans.3,6,7 Marburg virus and Ravn virus, a related pathogen, belong to a species called Orthomarburgvirus marburgense. Both Marburg and Ravn virus can cause the constellation of symptoms called Marburg virus disease.5
The Egyptian Fruit Bat (Rousettus aegyptiacus) is the prime suspect for being the primary natural host of Marburg virus.6 Indeed, researchers have isolated Marburg virus from R. aegyptiacus in Sierra Leone, Gabon, Uganda, Kenya, the Republic of South Africa and Zambia.6 Marburg virus does not seem to cause diseases in bats.5 In addition to bats and green monkeys, pigs can carry and shed Marburg virus after a bite from an infected bat. As a result, pigs can act as a reservoir of infections that can exacerbate outbreaks of Marburg virus disease.4,5
Marburg virus can spread rapidly to humans after direct contact with an infected animal, such as bats in caves and mines.2,4,5 Once Marburg virus jumps the species barrier, contact with bodily fluids or organs through broken skin or mucous membranes or exposure to contaminated surfaces, such as bedding and clothing, can spread Marburg virus.4,5 Marburg virus transmitted by contaminated injection equipment or needle-stick injuries can cause particularly severe symptoms.5 The fatality rate is high. However, burial rituals that involve direct contact with the corpses of infected people can further transmit Marburg virus.5
The incubation period for Marburg virus is between two and 21 days.5 Initial symptoms include fever, severe headaches, muscle aches and pains, and severe malaise. Gastrointestinal symptoms include nausea, vomiting, severe watery diarrhoea, cramps and abdominal pain.2,3,5 Some people develop a rash, confusion, irritability, aggression or orchitis (testicular inflammation).5
After about five days, symptoms can progress into severe haemorrhagic fever, including internal and external bleeding, organ failure and death between eight and nine days after symptoms emerged.2,3,5 In some outbreaks, mortality rates reached 88%.4 An analysis of 478 cases and 385 deaths from Marburg virus disease estimated a case fatality rate of 61.9%.2 Between 27 September and 8 November 2024, Rwanda reported 66 confirmed cases of Marburg virus from 7408 tests – 15 people died; a mortality rate of 23%.3 Healthcare workers accounted for most deaths from Marburg virus.8
While Marburg virus causes outbreaks, many more people seem to have been infected than develop serious symptoms. Serological studies determine if a person has an antibody to Marburg virus. A positive test strongly suggests they have been exposed to Marburg virus. In the Central African Republic, for example, between 1% and 7.4% (depending on the population subgroup) is seropositive.2 This may suggest that some outbreaks went undetected or that transmission can be asymptomatic. In addition, the serological test for Marburg virus may cross-react may with other pathogens.2 Further studies need to explore the infection’s natural history.
Currently, there are no approved vaccines or antivirals for Marburg virus.5 Vaccines are being developed often using technology and experience gained during the COVID-19 pandemic.2,3,5 Animal studies also suggest that obeldesivir, an antiviral, may be effective.8 Hopefully, at least some of these will be available, at least as part of clinical trials, during the next Marburg virus outbreak.
In the meantime, early supportive care including rehydration and treating symptoms as they emerge maximises the chance of survival.5 Basic measures, such as infection prevention and control, risk communication and community engagement, controlled outbreaks of Marburg virus disease in Equatorial Guinea and Tanzania during 2023.2 Nevertheless, the case fatality rate reached 75% and 62.5% in Equatorial Guinea and Tanzania respectively.3
Lessons
The prospect of being infected with Marburg virus is terrifying. But the outbreaks seem to be sporadic and, in general, isolated to parts of Africa. So, healthcare professionals can help keep the risks in perspective. For example, only two outbreaks involved more than 100 confirmed cases: 154 cases in the Democratic Republic of the Congo in 1998 and 254 cases in Angola in 2005.2
Travellers can take precautions to reduce their risk of contracting Marburg virus.5 In 2008, two independent cases were reported in travellers who visited colonies of R. aegyptiacus in a cave in Uganda.5 People visiting or working in mines or caves with fruit bat colonies should wear gloves, masks and other protective clothing.5 Sensible precautions also reduce the risk of other infections harboured by bats.9
There are more than 1400 species of bat ranging from the Giant Golden-crowned flying fox (Acerodon jubatus) with a 1.7 m wingspan to the Kitti’s Hog-nosed bat (Craseonycteris thonglongyai) with a wingspan of just 15 cm.9 Bats are found worldwide excepting Antarctica, the high Arctic and some remote islands.9
Bats may spread rabies, Ebola, Bombali and some other viruses, including influenza A (H17N10) and possibly SARS-CoV-2.7,9,10 Experimental studies suggest that bat flu viruses that acquire certain genes can infect human airway epithelial cells.10 But further research needs to characterise bats’ role in the transmission of diseases.5 Nevertheless, Marburg virus illustrates that ‘bats may be important hosts for future viral infectious diseases’.6
Marburg virus will probably continue to cause sporadic outbreaks in parts of Africa rather than develop into a global pandemic. Yet this relatively rare disease teaches all of us an important lesson. The Rwanda Marburg virus ‘outbreak sends a clear message [that] neglecting the interconnectedness of human, animal and environmental health leaves everyone vulnerable to future crises’.4 It’s not whether these future crises will occur. It’s when.
Mark Greener is a freelance medical writer
References
1. Downs W. Marburg Virus Disease. In: Kiple KF, editor. The Cambridge World History of Human Disease. Cambridge: Cambridge University Press; 1993. p. 862-5. https://doi.org.DOI: 10.1017/CHOL9780521332866.148
2. Cuomo-Dannenburg G, McCain K, McCabe R et al. (2024) Marburg virus disease outbreaks, mathematical models, and disease parameters: a systematic review. Lancet Infect Dis. 24 (5):e307-e17. https://doi.org.10.1016/s1473-3099(23)00515-7.
3. Sibomana O, Hakayuwa CM and Munyantore J. (2025) Marburg virus reaches Rwanda: how close are we to a vaccine solution? Inter J Infect Dis. 153. https://doi.org.10.1016/j.ijid.2024.107371.
4. Henley P and Shyaka A. (2025) The Marburg virus outbreak is a critical moment for Rwanda’s one health policy. Nat Med. https://doi.org.10.1038/s41591-024-03473-x.
5. WHO. (2025) Marburg virus disease. Available at https://www.who.int/news-room/fact-sheets/detail/Marburg-virus-disease. Accessed February 2025.
6. Liu Z, Liu Q, Wang H et al. (2024) Severe zoonotic viruses carried by different species of bats and their regional distribution. Clin Microbiol Infect. 30 (2):206-10. https://doi.org.10.1016/j.cmi.2023.09.025.
7. Bodmer BS, Breithaupt A, Heung M et al. (2023) In vivo characterization of the novel ebolavirus Bombali virus suggests a low pathogenic potential for humans. Emerg Microbes Infect. 12 (1):2164216. https://doi.org.10.1080/22221751.2022.2164216.
8. Cross RW, Woolsey C, Prasad AN et al. (2025) Oral obeldesivir provides postexposure protection against Marburg virus in nonhuman primates. Nature Medicine. https://doi.org.10.1038/s41591-025-03496-y.
9. Fenton M and Rydell J. (2023) A Miscellany of Bats. London: Pelagic Publishing.
10. Juozapaitis M, Aguiar Moreira É, Mena I et al. (2014) An infectious bat-derived chimeric influenza virus harbouring the entry machinery of an influenza A virus. Nature Comms. 5 (1):4448. https://doi.org.10.1038/ncomms5448.