Marburg Virus Disease: Are Vaccines and Treatments in the Horizon?

Marburg virus disease is back in the headlines. Outbreaks of this emerging disease are rare but highly dangerous. Fortunately, today we have more knowledge –and some tools in the horizon – that can help us contain them.

What is Marburg virus disease?

Marburg disease is caused by the Marburg virus, which belongs to the same family as the Ebola virus (filoviruses). The virus was first described in 1967 following an outbreak in laboratory staff in the cities of Marburg, Frankfurt and Belgrade. All three labs had received infected African green monkeys from Uganda.

Marburg virus is one of the pathogens identified by the WHO as having epidemic or pandemic potential and for which the development of diagnostic tests, vaccines and treatments needs to be accelerated.

How is it transmitted?

Like many emerging diseases, it is caused by a zoonotic virus. This means that it occasionally jumps from an animal reservoir (mainly bats of the genus Rousettus) to humans, through contact with faeces or by handling or eating infected animals. Once this jump has been made, the virus can be transmitted from person to person, although not efficiently. Close contact with the blood or body fluids of an infected person is required. It is not airborne and infected people are not contagious before symptoms appear.

What are the symptoms?

The incubation period (between infection and onset of symptoms) ranges from 2 to 21 days. The illness begins abruptly, with high fever, severe headache, and general malaise. There may also be muscle aches, abdominal pain, nausea, vomiting and diarrhoea. Many patients develop bleeding (nose, gums, faeces) after 5 to 7 days, as well as confusion or aggressiveness. Death usually occurs within 8 to 9 days of the onset of symptoms.

How deadly is it?

Marburg virus has a high case fatality rate of about 50%. However, the case fatality rate can vary depending on the strain of the virus and the quality of medical care received.

Is there any treatment for Marburg virus disease?

There is currently no specific treatment for the virus, but prompt medical care to treat symptoms and rehydrate the patient greatly increases the chances of survival. Some candidate treatments, such as the antiviral remdesivir or monoclonal antibodies, are ready for testing.

Is there a vaccine?

There is no approved vaccine for Marburg. The most advanced vaccine candidate is one developed by the Sabin Institute in the US, which uses a chimpanzee adenovirus to carry the instructions needed to make a viral protein. The vaccine has already been shown to be safe in an initial phase 1 trial and a phase 2 trial is currently underway in Uganda and Kenya.

What is happening in Rwanda?

Rwanda is currently facing its first outbreak of Marburg virus disease, with a total of 56 cases (mostly among health workers) and 12 deaths reported to date (7 October 2024). The country has good experience in dealing with infectious disease outbreaks. But the current situation is worrying because many of the cases have occurred near Kigali, a city of almost 1.5 million people. Therefore, there is a risk of the outbreak spreading within the city and to other countries in Africa, or beyond.

What is the risk for other countries?

The WHO warns there is a risk of the outbreak spreading to neighbouring countries (DRC, Tanzania, Uganda). The ECDC considers the risk of infection for people travelling to Rwanda to be low, although the possibility of an infected person travelling to Europe (as highlighted by a recent false alarm in Germany) cannot be ruled out. But even if this were to happen, the chances of an outbreak in Europe are very low, thanks to the virus’s limited transmissibility and the swift activation of response protocols when there is a suspected case.

What is being done?

The most urgent action right now is to provide all necessary support to Rwanda and neighbouring countries to control the outbreak before it claims more lives.

In this regard, the recent announcement by the US that 700 doses of the Sabin Institute's vaccine have reached the African country to begin clinical trials is a positive development. Rwandan scientists have been meeting with members of the Marburg virus vaccine consortium (MARVAC) to plan such trials, which will use the same ‘ring vaccination’ strategy that was used to test the Ebola vaccine: vaccinate - or not - close contacts of confirmed cases. The US also said it will send the experimental monoclonal antibody MBP-091 to be tested as a potential treatment.

“I’m gratified that the work that WHO has done has put the field in the position to be able to respond to an outbreak,” said Nancy Sullivan, director of Boston University's infectious diseases laboratory, in an interview with STATnews.

Once again, this outbreak underscores the urgency of preparing to ensure a global and coordinated response to emerging health threats, no matter where they occur.