Ebola and Marburg
Ebola and Marburg are closely related filoviruses, long filamentous single stranded RNA viruses that cause haemorrhagic fever. The mortality rate can be high, and viral clearance can be slow, with recent papers demonstrating that not only can Ebola infect neural cells, but can also persist in a human cerebral organoid model1. Other sites of persistence include the eyes, placenta, breast milk and semen.
Whilst close physical contact is required for transmission, survivors may be infectious for many months after clinical recovery, and transmission via contaminated objects is also possible. Fortunately, Ebola is not an airborne disease, although this possible evolution has been dramatized by Hollywood in films such as ‘Outbreak’. The natural primary hosts for Ebola are African fruit bats, but the virus can be contracted from handling other infected wildlife, including non-human primates, antelopes and porcupines – “bushmeat” can be an important local food source that creates opportunity for animal to human spill over.
Marburg was first described in Marburg, Germany, in 1967 after laboratory workers were exposed to infected African Green Monkeys. Marburg (MARD) has caused several outbreaks in recent years, in Ghana, Equatorial Guinea, Ethiopia and Tanzania 2
Sudan Virus Disease (SVD) is also closely related to Ebola, with outbreaks in Uganda and Sudan. Case fatality rates of the Sudan virus have ranged from 41-100% in past outbreaks. 3
Several strains of Ebola are known to exist:
Ebola Zaire has a case fatality rate of 60-100% and has a fast replication and viral load, triggering a cytokine storm and rapid cell death. Zaire was first recognised in 1976 in southern Sudan and near the Ebola river in Zaire, where there were over 500 cases, and a 70% mortality rate, with further outbreaks in the mid 1990’s, and most recently in 2025 in the Democratic Republic of the Congo 2
Ebola Bundibugyo is a milder strain compared to Zaire, but still has a case fatality rate of 25-50%. Bundibugyo was first discovered in 2007 in Uganda, however unlike Zaire, there are no approved vaccines or therapeutic drugs, as it is sufficiently distinct from Zaire that vaccines are not effective, and containment relies almost entirely on isolation, surveillance and basic supportive fluids as treatment.
