Marburg outbreaks: One of the world’s deadliest viruses

Rwanda is on alert after new cases of sickness caused by Marburg virus – one of the deadliest pathogens known – were reported in late September.
While outbreaks of the viral disease it causes are rare and usually confined to sub-Saharan Africa, four concerning incidences have occurred since 2021.
The most recent Rwandan outbreak has seen at least 36 cases of Marburg virus disease (MRV), with more than 400 people currently being monitored for symptoms.
Like many diseases, MRV’s name derives from when the disease was first reported in western countries, tracing back to lab outbreaks in Germany and the former Yugoslavia in 1967.
Back then, a delivery of vervet monkeys (Chlorocebus pygerythrus) to labs in Marburg and Frankfurt in Germany, and Belgrade in what is present-day Serbia, was pinpointed as the source of the outbreak.
Patients admitted to hospitals displayed a range of symptoms common to many viral diseases, but those who died showed signs of hemorrhagic fever.
Current statistics indicate an 88% mortality rate among those infected with MRV. While outbreaks and infections are infrequent compared to some other viruses in the region, it’s often lethal.
After its first reported outbreaks in Germany and Serbia in the 1960s, most subsequent outbreaks have been reported in sub-Saharan Africa. These include Angola (Uige, 2005), Guinea (Gueckedou, 2021), Ghana (Ashanti Region, 2022), Equatorial Guinea (Kie-Ntem, 2023) and repeat outbreaks across the Democratic Republic of the Congo (1998-2000), Uganda (2007, 2008, 2012, 2014, 2017), Tanzania (2023) and Kenya (1980, 1987).
Johannesburg in South Africa also reported an outbreak of the disease in 1975.
Marburg virus can spread very quickly in the body, infecting and destroying cells in the blood, liver and skin.
Once someone is infected, the virus incubates for five to ten days. It then presents with sudden onset of fever, headache and muscle pain, as well as bleeding in the skin and mucous membranes. The mouth, eyes, gastrointestinal tract and internal organs are often affected, too.
In severe cases, people can experience neurological paralysis. Coagulation disorders associated with the virus can cause what is known as hemorrhagic shock. That can lead to organ and circulatory failure and death. Without intensive medical care, most infected people die.
Like many viruses, Marburg virus is ‘zoonotic’, which means it is able to jump from an animal host reservoir to humans through prolonged exposure. In the case of Marburg, cave and mine-dwelling rousette bats are the most common source of transmission.
Once in humans, the virus is transmitted through bodily fluids such as blood, urine or saliva.
Outside the body, however, the viruses do not last long and droplet infections through the air are extremely rare.
Patients usually need intensive medical care and must be isolated because of the high risk of infection. So far, however, it’s only possible to treat the symptoms of the virus.
The most common treatments include infusions to prevent fluid loss, with electrolytes to replace blood salts and glucose to regulate sugar balance.
Drugs are also used to stabilize blood pressure, reduce fever or stop diarrhea and vomiting. Patients may also receive a blood transfusion and clotting agents to slow and stop any extreme loss of blood.
These measures increase the infected person’s chances of survival, but the disease is still fatal in about half of all cases. Death usually occurs eight to nine days after the onset of the disease and is often the result of severe blood loss.
Antiviral drugs such as remdesivir have been used in clinical trials to treat Ebola and could also be tested against Marburg fever.
There is currently no specific treatment or vaccine to address Marburg virus disease. The Rwandan health ministry reported trials for a vaccine were due to start shortly after the first reports in the country, though with few details.
There are at least two similarly named research consortiums racing to develop an effective vaccine.
The first is the primarily US-based ‘MARVAC’, a WHO-coordinated group. Its members have several vaccines in the pipeline. One candidate in development by the National Institute of Allergy and Infectious Diseases in the US uses a chimpanzee adenovirus. Called cAd3, this deactivated adenovirus has a surface protein that has been shown to trigger an immune response to Marburg. During a first-phase trial, 40 adult volunteers were given the vaccine. A majority showed a “robust antibody response” that was maintained for nearly a year.
At the end of 2023, the European Commission granted another consortium (calling itself ‘MARVAX’), €7.4m to develop their own vaccine product. This group includes research contributions from France’s Institut Pasteur, Spain’s National Centre for Biotechnology and CZ Vaccines, and Germany’s Bernhard Nocht Institute for Tropical Medicine.
This story was substantially updated from the original published on 16 February 2023.
Sources:
WHO Africa Region https://www.afro.who.int/health-topics/marburg-haemorrhagic-fever
Robert W. Cross et al (2022). “An introduction to the Marburg virus vaccine consortium, MARVAC”. PLoS Pathogens. https://doi.org/10.1371%2Fjournal.ppat.1010805