One of the deadliest viruses in the world – DW – October 4th, 2024

Rwanda is on alert after new cases of the Marburg virus – one of the deadliest known pathogens – were reported in late September.

While outbreaks of the viral disease it causes are rare and usually limited to sub-Saharan Africa, there have been four worrisome incidents since 2021.

The recent outbreak in Rwanda has seen at least 36 cases of Marburg virus disease (MRV), with more than 400 people currently being monitored for symptoms.

As with many diseases, MRV's name derives from when the disease was first reported in Western countries, dating back to laboratory outbreaks in Germany and the former Yugoslavia in 1967.

At that time a delivery of vervet monkeys (Chlorocebus pygerythrus) in laboratories in Marburg and Frankfurt in Germany and Belgrade in modern-day Serbia was identified as the source of the outbreak.

Patients admitted to hospitals showed a range of symptoms common to many viral diseases, but those who died showed signs of hemorrhagic fever.

Marburg is one of the 10 deadliest virus infections worldwide

Current statistics show an 88% mortality rate for those infected with MRV. While outbreaks and infections are rare compared to some other viruses in the region, they are often fatal.

After the first reported outbreaks in Germany and Serbia in the 1960s, most subsequent outbreaks were reported in sub-Saharan Africa. These include Angola (Uige, 2005), Guinea (Gueckedou, 2021), Ghana (Ashanti Region, 2022), Equatorial Guinea (Kie-Ntem, 2023) and repeated outbreaks in the Democratic Republic of Congo (1998-2000) and Uganda (2007 , 2008, 2012, 2014, 2017), Tanzania (2023) and Kenya (1980, 1987).

Johannesburg, South Africa also reported an outbreak of the disease in 1975.

The symptoms of the Marburg virus

The Marburg virus can spread very quickly throughout the body, infecting and destroying cells in the blood, liver and skin.

Once someone is infected, the virus incubates for five to 10 days. This is followed by sudden fever, headaches and muscle pain as well as bleeding in the skin and mucous membranes. The mouth, eyes, gastrointestinal tract and internal organs are also often affected.

In severe cases, neurological paralysis can occur. Clotting disorders associated with the virus can cause a condition called hemorrhagic shock. This can lead to organ and circulatory failure and death. Without intensive care, most infected people die.

How is the Marburg virus transmitted?

Like many viruses, Marburg virus is “zoonotic,” meaning it can jump from an animal host reservoir to humans through prolonged exposure. In the case of Marburg, cave and mine bats are the most common source of transmission.

In humans, the virus is transmitted through body fluids such as blood, urine or saliva.

However, the viruses do not survive long outside the body and airborne droplet infections are extremely rare.

How is Marburg virus treated?

Patients usually require intensive care and must be isolated due to the high risk of infection. However, so far it is 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 levels.

Medications are also used to stabilize blood pressure, reduce fever, or stop diarrhea and vomiting. Patients may also receive a blood transfusion and clotting medications to slow and stop extreme blood loss.

These measures increase the infected person's chances of survival, but the disease is fatal in around 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.

Is a vaccine against the Marburg virus in development?

There is currently no specific treatment or vaccination for Marburg virus disease. The Rwandan Health Ministry reported that trials for a vaccine were expected to begin shortly after the first reports in the country, although with few details.

There are at least two research consortia of the same name fighting to develop an effective vaccine.

The first is the mainly US-based “MARVAC”, a group coordinated by the WHO. Its members have several vaccines in the pipeline. One candidate, being developed by the National Institute of Allergy and Infectious Diseases in the US, uses a chimpanzee adenovirus. This deactivated adenovirus, called cAd3, has a surface protein that has been shown to trigger an immune response against Marburg. During an initial trial phase, 40 adult volunteers received the vaccine. The majority showed a “robust antibody response” that lasted for almost a year.

At the end of 2023, the European Commission awarded another consortium (calling itself “MARVAX”) €7.4 million to develop its own vaccine product. This group includes research contributions from the French Institut Pasteur, the Spanish National Center for Biotechnology and CZ Vaccines, and the German Bernhard Nocht Institute for Tropical Medicine.

This story has been significantly updated from the original published on February 16, 2023.

Sources:

WHO Africa Region

Robert W. Cross et al. (2022). “An introduction to the Marburg virus vaccine consortium MARVAC”. PLoS pathogens.