Viral hemorrhagic fevers (VHFs) refers to a group of rare, potentially lethal viral infections which can cause severe illness in humans.
VHFs are caused by five different families of viruses:
- Filoviruses (such as Ebola virus, Marburg virus)
- Flaviviruses (such as Dengue virus, Yellow fever)
- Arenaviruses (such as Lassa fever, Machupo virus)
- Bunyaviruses (such as Crimean Congo hemorrhagic fever, Rift Valley fever)
- Paramyxoviruses (such as Nipah virus, Hendra virus)
Viral hemorrhagic fevers (VHFs) are endemic in parts of Africa, South America, the Middle East, and Eastern Europe. Such viruses are found naturally in reservoir hosts, most commonly nonhuman primates, bats, rodents and insects. A human outbreak of VHF typically begins through direct contact with a reservoir host or their secretions. Once a human is infected, spread of the disease can occur through direct contact with an infected person and/or their bodily fluids. Exposure to body fluids occurs in high-risk scenarios, such as providing care in a home or healthcare setting, participating in corpse contact funeral rituals, and working in a laboratory where human specimens are handled.
The symptoms of both Marburg and Ebola are very similar. The onset of symptoms typically occurs after an incubation period of 2-21 days after exposure. Symptoms initially present nonspecifically as fever, fatigue, body aches, headaches, and gastrointestinal upset (nausea, vomiting and diarrhea). Severe symptoms can appear quickly after initial onset and includes dehydration, septic shock, multi-organ failure, seizures, coma and most recognizably, bleeding. VHFs cause bleeding by damaging blood vessels and preventing the patient's blood from clotting; however, it is important to note that not every VHF patient experiences bleeding, and even when they do, it rarely causes death. It is vital to provide a detailed travel history for patients under investigation for any VHFs in order to provide infection prevention for hospital staff and any relevant epidemiological information
Named after the geographic locations in which they were isolated, four genetically distinct strains of pathogenic Ebola have been identified since its initial discovery in 1976: Zaire (EBOV), Sudan (SUDV), Tai Forest (TAFV) and Bundibugyo (BVBD). Two additional strains, Reston (RESTV) and Bombali (BOMV), are not known to cause disease in humans. The Zaire strain is the most lethal and has caused the greatest number of outbreaks, including the West African Ebola virus epidemic in 2014. More recent outbreaks of Ebola have been caused by the Sudan strain.
Marburg virus is less genetically diverse, as only two strains have been isolated since its discovery in 1967: Marburg (MARV) and Ravn (RAVV). Recent outbreaks of Marburg virus occurred in Rwanda (September 2024) and Tanzania (January 2025).
